Oracle SQL Tutorial Study Material SQL Queries Interview Questions and Answers Freshers and Experienced with examples

By | February 19, 2017

Oracle SQL Tutorial Study Material SQL Queries Interview Questions and Answers Freshers and Experienced with examples

Oracle SQL Tutorial SQL Study Material SQL Queries SQL Interview Questions and Answers with examples SQL Basics for Beginners and Experienced Oracle SQL Tutorial Oracle SQL Interview Questions Oracle SQL Queries with Examples SQL Scenarios

FUNCTIONS

Functions can be categorized as follow

  • Single row functions
  • Group functions

SINGLE ROW FUNCTIONS

Single row functions can be categorized into five. These will be applied for each row and produces individual output for each row

  • Numeric functions
  • String functions
  • Date functions
  • Miscellaneous functions
  • Conversion functions

NUMERIC FUNCTIONS

  • Abs
  • Sign
  • Sqrt
  • Mod
  • Nvl
  • Power
  • Exp
  • Ln
  • Log
  • Ceil
  • Floor
  • Round
  • Trunk
  • Bitand
  • Greatest
  • Least
  • Coalesce




  1. a) ABS

     Absolute value is the measure of the magnitude of value.

     Absolute value is always a positive number.

     Syntax: abs (value)

     Ex:

          SQL> select abs(5), abs(-5), abs(0), abs(null) from dual;

 

                     ABS(5)    ABS(-5)     ABS(0)  ABS(NULL)

                     ———- ———-    ———- ————-

                          5              -5                0

 

  1. b) SIGN

     Sign gives the sign of a value.

     Syntax: sign (value)




     Ex:

          SQL> select sign(5), sign(-5), sign(0), sign(null) from dual;

 

                        SIGN(5)   SIGN(-5)    SIGN(0) SIGN(NULL)

———-   ———-     ———- ————–

       1            -1          0

 

  1. c) SQRT

     This will give the square root of the given value.

     Syntax: sqrt (value)      —  here value must be positive.

     Ex:

          SQL> select sqrt(4), sqrt(0), sqrt(null), sqrt(1) from dual;

 

                        SQRT(4)    SQRT(0) SQRT(NULL)    SQRT(1)

———-    ———- —————    ———-

         2               0                                            1

 

  1. d) MOD

     This will give the remainder.

     Syntax: mod (value, divisor)  

     Ex:

          SQL> select mod(7,4), mod(1,5), mod(null,null), mod(0,0), mod(-7,4) from dual;

 

                        MOD(7,4)   MOD(1,5) MOD(NULL,NULL)   MOD(0,0)  MOD(-7,4)

————   ———-  ———————    ———– ————-

         3               1                                            0         -3

 

  1. e) NVL

 

     This will substitutes the specified value in the place of null values.

 

     Syntax: nvl (null_col, replacement_value)  

 

     Ex:

          SQL> select * from student;            — here for 3rd row marks value is null

 

                         NO NAME      MARKS

 — ——-      ———

                          1        a         100

                          2        b          200

                          3        c

 




SQL> select no, name, nvl(marks,300) from student;

 

 

                        NO NAME  NVL(MARKS,300)

—  ——-  ———————

           1           a             100

                       2           b             200

           3           c             300

 

SQL> select nvl(1,2), nvl(2,3), nvl(4,3), nvl(5,4) from dual;

 

  NVL(1,2)   NVL(2,3)   NVL(4,3)   NVL(5,4)

  ———-    ———-    ———-    ———-

         1               2                    4                   5

 

SQL> select nvl(0,0), nvl(1,1), nvl(null,null), nvl(4,4) from dual;

 




  NVL(0,0)   NVL(1,1) NVL(null,null)  NVL(4,4)

  ———-    ———- —————–   ———-

         0              1                                                  4

 

  1. f) POWER

 

     Power is the ability to raise a value to a given exponent.

 

     Syntax: power (value, exponent)      

 

     Ex:

          SQL> select power(2,5), power(0,0), power(1,1), power(null,null), power(2,-5) from 

                  dual;

 

POWER(2,5) POWER(0,0) POWER(1,1) POWER(NULL,NULL) POWER(2,-5)

————–  ————–  —– ——— ———————–  —————

        32                    1                  1                                                     .03125

 

  1. g) EXP

 




     This will raise e value to the give power.

 

     Syntax: exp (value)      

 

     Ex:

          SQL> select exp(1), exp(2), exp(0), exp(null), exp(-2) from dual;

 

                        EXP(1)           EXP(2)           EXP(0)  EXP(NULL)    EXP(-2)

——–            ———           ——–  ————-    ———-

2.71828183  7.3890561          1                          .135335283

 

  1. h) LN

 

     This is based on natural or base e logarithm.

 

     Syntax: ln (value)           — here value must be greater than zero which is positive only.

 




     Ex:

          SQL> select ln(1), ln(2), ln(null) from dual;

 

                        LN(1)      LN(2)      LN(NULL)

——-      ——-      ————

                            0        .693147181

 

          Ln and Exp are reciprocal to each other.

            EXP (3) = 20.0855369

            LN (20.0855369) = 3

 

  1. i) LOG

 




    This is based on 10 based logarithm.

 

    Syntax: log (10, value)   — here value must be greater than zero which is positive only.      

 

    Ex:

          SQL> select log(10,100), log(10,2), log(10,1), log(10,null) from dual;

 

LOG(10,100)  LOG(10,2)  LOG(10,1) LOG(10,NULL)

—————   ———–   ————  —————–

                             2            .301029996          0

 

LN (value) = LOG (EXP(1), value)




 

SQL> select  ln(3), log(exp(1),3) from dual;

 

                        LN(3)      LOG(EXP(1),3)

——-      —————–

1.09861229    1.09861229

 

  1. j) CEIL

 

     This will produce a whole number that is greater than or equal to the specified value.

 

     Syntax: ceil (value)       

 




     Ex:

          SQL> select ceil(5), ceil(5.1), ceil(-5), ceil( -5.1), ceil(0), ceil(null) from dual;

 

                        CEIL(5)  CEIL(5.1)   CEIL(-5) CEIL(-5.1)    CEIL(0) CEIL(NULL)

———  ———–    ———- ————     ——–  ————–

                                5            6                -5            -5                 0

 

  1. k) FLOOR

 

     This will produce a whole number that is less than or equal to the specified value.

 

     Syntax: floor (value)    

 

     Ex:

          SQL> select floor(5), floor(5.1), floor(-5), floor( -5.1), floor(0), floor(null) from dual;

 




                        FLOOR(5) FLOOR(5.1)  FLOOR(-5) FLOOR(-5.1)   FLOOR(0) FLOOR(NULL)

———–  ————-   ————  ————–    ———–  —————-

         5               5                 -5                 -6                   0

 

  1. l) ROUND

 

    This will rounds numbers to a given number of digits of precision.

 

     Syntax: round (value, precision)       

 

     Ex:

          SQL> select round(123.2345), round(123.2345,2), round(123.2354,2) from dual;




 

        ROUND(123.2345)  ROUND(123.2345,0) ROUND(123.2345,2) ROUND(123.2354,2)

                   ———————   ————————  ———————–  ———————–

                                123                          123                            123.23                      123.24

 

            SQL> select round(123.2345,-1), round(123.2345,-2), round(123.2345,-3),

                  round(123.2345,-4) from dual;

   

ROUND(123.2345,-1) ROUND(123.2345,-2) ROUND(123.2345,-3) ROUND(123.2345,-4)

           ————————  ————————-  ————————   ————————

                           120                                100                            0                                         0

 

SQL> select round(123,0), round(123,1), round(123,2) from dual;

 

ROUND(123,0) ROUND(123,1) ROUND(123,2)

—————–  —————–  —————-

         123                   123                               123

 

SQL> select round(-123,0), round(-123,1), round(-123,2) from dual;

 

ROUND(-123,0) ROUND(-123,1) ROUND(-123,2)

——————  —————–   ——————-

                                -123                 -123                    -123

 




SQL> select round(123,-1), round(123,-2), round(123,-3), round(-123,-1), round(-123,- 

        2), round(-123,-3) from dual;

 

ROUND(123,-1) ROUND(123,-2) ROUND(123,-3) ROUND(-123,-1) ROUND(-123,-2)          

ROUND(-123,-3)

           ————- ————- ————- ————– ————– ————–

                     120           100             0               -120               -100              0

 

SQL> select round(null,null), round(0,0), round(1,1), round(-1,-1), round(-2,-2) from

          dual;

 

ROUND(NULL,NULL) ROUND(0,0) ROUND(1,1) ROUND(-1,-1) ROUND(-2,-2)

———————–  ————–  ————–  —————-  —————-

                                                                        0                       1                   0                    0

     

  1. m) TRUNC

 

      This will truncates or chops off digits of precision from a number.

 

      Syntax: trunc (value, precision)       

 




      Ex:

          SQL> select trunc(123.2345), trunc(123.2345,2), trunc(123.2354,2) from dual;

 

TRUNC(123.2345) TRUNC(123.2345,2) TRUNC(123.2354,2)

———————  ———————–  ———————–

            123                        123.23                     123.23

 

SQL> select trunc(123.2345,-1), trunc(123.2345,-2), trunc(123.2345,-3),

         trunc(123.2345,-4) from dual;

 

TRUNC(123.2345,-1) TRUNC(123.2345,-2) TRUNC(123.2345,-3) TRUNC(123.2345,-4)

————————  ————————   ———————–  ————————

               120                              100                                0                             0

 

SQL> select trunc(123,0), trunc(123,1), trunc(123,2) from dual;

 

TRUNC(123,0) TRUNC(123,1) TRUNC(123,2)

—————-   —————-  —————–

         123                    123                 123

 

SQL> select trunc(-123,0), trunc(-123,1), trunc(-123,2) from dual;

 

TRUNC(-123,0) TRUNC(-123,1) TRUNC(-123,2)

—————–   —————–  —————–

         -123                    -123                -123

 

SQL> select trunc(123,-1), trunc(123,-2), trunc(123,-3), trunc(-123,-1), trunc(-123,2),

         trunc(-123,-3) from dual;

 




TRUNC(123,-1) TRUNC(123,-2) TRUNC(123,-3) TRUNC(-123,-1) TRUNC(-123,2) TRUNC(-

123,-3)

————- ————- ————- ————– ————- ————–

          120           100             0                   -120          -123              0

 

SQL> select trunc(null,null), trunc(0,0), trunc(1,1), trunc(-1,-1), trunc(-2,-2) from dual;

 

TRUNC(NULL,NULL) TRUNC(0,0) TRUNC(1,1) TRUNC(-1,-1) TRUNC(-2,-2)

———————–  ————-  ————-  —————  —————-

                                                       0                   1                     0                      0

 

  1. n) BITAND

 

     This will perform bitwise and operation.

 

     Syntax: bitand (value1, value2)         

 

     Ex:

          SQL> select bitand(2,3), bitand(0,0), bitand(1,1), bitand(null,null), bitand(-2,-3) from

                   dual;

BITAND(2,3) BITAND(0,0) BITAND(1,1) BITAND(NULL,NULL) BITAND(-2,-3)

————–  —————  ————–   ————————  —————–

          2           0                      1                                                          -4

 

  1. o) GREATEST

 




     This will give the greatest number.

 

     Syntax: greatest (value1, value2, value3 … valuen)         

 

     Ex:

          SQL> select greatest(1, 2, 3), greatest(-1, -2, -3) from dual;

 

GREATEST(1,2,3) GREATEST(-1,-2,-3)

——————–  ———————–

              3                    -1

 

  • If all the values are zeros then it will display zero.
  • If all the parameters are nulls then it will display nothing.
  • If any of the parameters is null it will display nothing.

 

  1. p) LEAST

 

    This will give the least number.

 

    Syntax: least (value1, value2, value3 … valuen)     

 

     Ex:

          SQL> select least(1, 2, 3), least(-1, -2, -3) from dual;

 




LEAST(1,2,3)         LEAST(-1,-2,-3)

——————–  ———————–

              1                    -3

  • If all the values are zeros then it will display zero.
  • If all the parameters are nulls then it will display nothing.
  • If any of the parameters is null it will display nothing.
  1. q) COALESCE

 

    This will return first non-null value.

 

    Syntax: coalesce (value1, value2, value3 … valuen)          

 

     Ex:

            SQL> select coalesce(1,2,3), coalesce(null,2,null,5) from dual;

 

COALESCE(1,2,3) COALESCE(NULL,2,NULL,5)

——————-   ——————————-

              1                                            2

 




STRING FUNCTIONS

 

  • Initcap
  • Upper
  • Lower
  • Length
  • Rpad
  • Lpad
  • Ltrim
  • Rtrim
  • Trim
  • Translate
  • Replace
  • Soundex
  • Concat ( ‘ || ‘ Concatenation operator)
  • Ascii
  • Chr
  • Substr
  • Instr
  • Decode
  • Greatest
  • Least
  • Coalesce
  1. a) INITCAP

 

     This will capitalize the initial letter of the string.

 

     Syntax: initcap (string)

 




     Ex:

          SQL> select initcap(‘computer’) from dual;

 

INITCAP

———–

Computer

 

  1. b) UPPER

 

     This will convert the string into uppercase.

 

     Syntax: upper (string)

 

     Ex:

          SQL> select upper(‘computer’) from dual;

UPPER

———–

COMPUTER

 

  1. c) LOWER

 




     This will convert the string into lowercase.

 

     Syntax: lower (string)

 

     Ex:

          SQL> select lower(‘COMPUTER‘) from dual;

LOWER

———–

computer

 

  1. d) LENGTH

 

     This will give length of the string.

 

     Syntax: length (string)

 

     Ex:

          SQL> select length(‘computer’) from dual;

 




LENGTH

———–

       8

 

  1. e) RPAD

 

     This will allows you to pad the right side of a column with any set of characters.

 

     Syntax: rpad (string, length [, padding_char])

 

     Ex:

          SQL> select rpad(‘computer’,15,’*’), rpad(‘computer’,15,’*#’) from dual;

 

RPAD(‘COMPUTER’  RPAD(‘COMPUTER’

———————-  ———————-

computer*******    computer*#*#*#*

 

— Default padding character was blank space.

 

  1. f) LPAD

 

     This will allows you to pad the left side of a column with any set of characters.

     Syntax: lpad (string, length [, padding_char])

 




     Ex:

          SQL> select lpad(‘computer’,15,’*’), lpad(‘computer’,15,’*#’) from dual;

 

LPAD(‘COMPUTER’  LPAD(‘COMPUTER’

———————   ———————

*******computer   *#*#*#*computer

 

— Default padding character was blank space.

 

  1. g) LTRIM

 

     This will trim off unwanted characters from the left end of string.

 

     Syntax: ltrim (string  [,unwanted_chars])

 

     Ex:

          SQL> select ltrim(‘computer’,’co’), ltrim(‘computer’,’com’) from dual;

 

LTRIM(  LTRIM

——–  ———

mputer   puter

 

SQL> select ltrim(‘computer’,’puter’), ltrim(‘computer’,’omputer’) from dual;

 

LTRIM(‘C  LTRIM(‘C

———-   ———-

computer   computer

          

           — If you haven’t specify any unwanted characters it will display entire string.

 

  1. h) RTRIM

 




     This will trim off unwanted characters from the right end of string.

 

     Syntax: rtrim (string [, unwanted_chars])

 

     Ex:

          SQL> select rtrim(‘computer’,’er’), rtrim(‘computer’,’ter’) from dual;

RTRIM(  RTRIM

——–  ———

comput   compu

 

SQL> select rtrim(‘computer’,’comput’), rtrim(‘computer’,’compute’) from dual;

 

RTRIM(‘C  RTRIM(‘C

———-   ———-

computer   computer

           — If you haven’t specify any unwanted characters it will display entire string.

 

  1. i) TRIM

 

     This will trim off unwanted characters from the both sides of string.

 

     Syntax: trim (unwanted_chars from string)

 




     Ex:

          SQL> select trim( ‘i’ from ‘indiani’) from dual;

 

TRIM(

—–

ndian

         

SQL> select trim( leading’i’ from ‘indiani’) from dual; — this will work as LTRIM

 

TRIM(L

——

ndiani

 

 

SQL> select trim( trailing’i’ from ‘indiani’) from dual; — this will work as RTRIM

 

TRIM(T

——

Indian

 

  1. j) TRANSLATE

 

     This will replace the set of characters, character by character.

 

     Syntax: translate (string, old_chars, new_chars)

 

     Ex:

          SQL> select translate(‘india’,’in’,’xy’) from dual;

 




TRANS

——–

xydxa

 

  1. k) REPLACE

 

     This will replace the set of characters, string by string.

 

     Syntax: replace (string, old_chars [, new_chars])

 

     Ex:

          SQL> select replace(‘india’,’in’,’xy’), replace(‘india’,’in’) from dual;

 

REPLACE   REPLACE

———–  ———–

Xydia         dia

 

  1. l) SOUNDEX

 

    This will be used to find words that sound like other words, exclusively used in where clause.

    Syntax: soundex (string)

 

    Ex:

         SQL> select * from emp where soundex(ename) = soundex(‘SMIT’);




 

     EMPNO ENAME      JOB              MGR HIREDATE         SAL     DEPTNO

     ——–  ——–      —–             —–  ————      ——— ———-

      7369    SMITH      CLERK         7902   17-DEC-80        500         20

 

  1. m) CONCAT

 

    This will be used to combine two strings only.

 

    Syntax: concat (string1, string2)

 

    Ex:

         SQL> select concat(‘computer’,’ operator’) from dual;

 

CONCAT(‘COMPUTER’

————————-

computer operator

 




    If you want to combine more than two strings you have to use concatenation operator (||).

 

         SQL> select ‘how’ || ‘ are’ || ‘ you’ from dual;

 

‘HOW’||’ARE

—————

how are you

 

  1. n) ASCII

 

    This will return the decimal representation in the database character set of the first

     character of the string.

 

    Syntax: ascii (string)

 

    Ex:

         SQL> select ascii(‘a’), ascii(‘apple’) from dual;

 

ASCII(‘A’)  ASCII(‘APPLE’)

————  ——————

        97             97

 

  1. o) CHR

 

    This will return the character having the binary equivalent to the string in either the

    database character set or the national character set.

 




    Syntax: chr (number)

 

    Ex:

         SQL> select chr(97) from dual;

 

CHR

—–

   a

 

  1. p) SUBSTR

 

     This will be used to extract substrings.

 

     Syntax: substr (string, start_chr_count [, no_of_chars])

 

     Ex:

SQL> select substr(‘computer’,2), substr(‘computer’,2,5), substr(‘computer’,3,7) from

         dual;

 

SUBSTR(  SUBST  SUBSTR

———-  ——-   ——–

omputer  omput   mputer

  • If no_of_chars parameter is negative then it will display nothing.
  • If both parameters except string are null or zeros then it will display nothing.
  • If no_of_chars parameter is greater than the length of the string then it ignores and calculates based on the orginal string length.
  • If start_chr_count is negative then it will extract the substring from right end.

 

1          2          3          4          5          6          7          8

 

C          O         M         P          U         T          E          R

 

                               -8 -7        -6        -5        -4        -3        -2        -1

 

  1. q) INSTR

 




     This will allows you for searching through a string for set of characters.

 

     Syntax: instr (string, search_str [, start_chr_count [, occurrence] ])

 

     Ex:

          SQL> select instr(‘information’,’o’,4,1), instr(‘information’,’o’,4,2) from dual;

 

INSTR(‘INFORMATION’,’O’,4,1) INSTR(‘INFORMATION’,’O’,4,2)

————————————  ————————————-

                           4                                           10

 

  • If you are not specifying start_chr_count and occurrence then it will start search from

      the beginning and finds first occurrence only.

  • If both parameters start_chr_count and occurrence are null, it will display nothing.

 

  1. r) DECODE

 




    Decode will act as value by value substitution.

    For every value of field, it will checks for a match in a series of if/then tests.

 

    Syntax: decode (value, if1, then1, if2, then2, ……. else);

 

    Ex:

          SQL> select sal, decode(sal,500,’Low’,5000,’High’,’Medium’) from emp;

 

       SAL     DECODE

                                                 —–    ———

       500           Low

      2500         Medium

      2000         Medium

      3500         Medium

      3000         Medium

      5000         High

      4000         Medium

      5000         High

      1800         Medium

      1200         Medium

      2000         Medium

      2700         Medium

      2200         Medium

      3200         Medium 

 

SQL> select decode(1,1,3), decode(1,2,3,4,4,6) from dual;

 

 

DECODE(1,1,3) DECODE(1,2,3,4,4,6)

—————–  ————————

            3                      6

 

  • If the number of parameters are odd and different then decode will display nothing.
  • If the number of parameters are even and different then decode will display last

      value.




  • If all the parameters are null then decode will display nothing.
  • If all the parameters are zeros then decode will display zero.

 

  1. s) GREATEST

 

     This will give the greatest string.

 

     Syntax: greatest (strng1, string2, string3 … stringn)      

 

     Ex:

           SQL> select greatest(‘a’, ‘b’, ‘c’), greatest(‘satish’,’srinu’,’saketh’) from dual;

 

 

GREAT GREAT

——-  ——-

    c         srinu

 

  • If all the parameters are nulls then it will display nothing.
  • If any of the parameters is null it will display nothing.

 

  1. t) LEAST

 




    This will give the least string.

 

    Syntax: greatest (strng1, string2, string3 … stringn)       

 

    Ex:

           SQL> select least(‘a’, ‘b’, ‘c’), least(‘satish’,’srinu’,’saketh’) from dual;

 

 

LEAST LEAST

——-  ——-

    a         saketh

 

  • If all the parameters are nulls then it will display nothing.
  • If any of the parameters is null it will display nothing.

 

  1. u) COALESCE

 

    This will gives the first non-null string.

 

    Syntax: coalesce (strng1, string2, string3 … stringn)       

 

    Ex:

         SQL> select coalesce(‘a’,’b’,’c’), coalesce(null,’a’,null,’b’) from dual;

 

COALESCE COALESCE

———–   ———–

       a                  a

 

DATE FUNCTIONS




 

  • Sysdate
  • Current_date
  • Current_timestamp
  • Systimestamp
  • Localtimestamp
  • Dbtimezone
  • Sessiontimezone
  • To_char
  • To_date
  • Add_months
  • Months_between
  • Next_day
  • Last_day
  • Extract
  • Greatest
  • Least
  • Round
  • Trunc
  • New_time
  • Coalesce

 

Oracle default date format is DD-MON-YY.

We can change the default format to our desired format by using the following command.

 

SQL> alter session set nls_date_format = ‘DD-MONTH-YYYY’;

        But this will expire once the session was closed.




 

  1. a) SYSDATE

 

     This will give the current date and time.

      Ex:

           SQL> select sysdate from dual;

 

SYSDATE

———–

24-DEC-06

 

  1. b) CURRENT_DATE

 

     This will returns the current date in the session’s timezone.

 

      Ex:

           SQL> select current_date from dual;

 

CURRENT_DATE

——————

     24-DEC-06

 

  1. c) CURRENT_TIMESTAMP

 

     This will returns the current timestamp with the active time zone information.

 

      Ex:

           SQL> select current_timestamp from dual;

 




CURRENT_TIMESTAMP

—————————————————————————

24-DEC-06 03.42.41.383369 AM +05:30

 

  1. d) SYSTIMESTAMP

 

     This will returns the system date, including fractional seconds and time zone of the

      database.

 

      Ex:

           SQL> select systimestamp from dual;

SYSTIMESTAMP

—————————————————————————

24-DEC-06 03.49.31.830099 AM +05:30

 

  1. e) LOCALTIMESTAMP

 

     This will returns local timestamp in the active time zone information, with no time zone

      information shown.

 

      Ex:

                   SQL> select localtimestamp from dual;

 

LOCALTIMESTAMP

—————————————————————————

24-DEC-06 03.44.18.502874 AM

 

  1. f) DBTIMEZONE

 




    This will returns the current database time zone in UTC format. (Coordinated Universal Time)

 

    Ex:

                   SQL> select dbtimezone from dual;

 

DBTIMEZONE

—————

   -07:00 

 

  1. g) SESSIONTIMEZONE

 

    This will returns the value of the current session’s time zone.

 

    Ex:

         SQL> select sessiontimezone from dual;

 




SESSIONTIMEZONE

—————————————————————————

+05:30   

  1. h) TO_CHAR

    This will be used to extract various date formats.

    The available date formats as follows.

    Syntax: to_char (date, format)

    DATE FORMATS

            D                      —         No of days in week

            DD                    —         No of days in month

            DDD                 —         No of days in year

            MM                   —         No of month

            MON                 —         Three letter abbreviation of month

            MONTH             —         Fully spelled out month

            RM                   —         Roman numeral month

            DY                    —         Three letter abbreviated day

            DAY                  —         Fully spelled out day

            Y                      —         Last one digit of the year

            YY                    —         Last two digits of the year

            YYY                  —         Last three digits of the year

            YYYY                —         Full four digit year

            SYYYY  —         Signed year

            I                       —         One digit year from ISO standard

            IY                     —         Two digit year from ISO standard

            IYY                   —         Three digit year from ISO standard




            IYYY                 —         Four digit year from ISO standard

            Y, YYY              —         Year with comma

            YEAR                —         Fully spelled out year

            CC                    —         Century

            Q                      —         No of quarters

            W                     —         No of weeks in month

            WW                  —         No of weeks in year

            IW                    —         No of weeks in year from ISO standard

            HH                    —         Hours

            MI                    —         Minutes

            SS                    —         Seconds

            FF                     —         Fractional seconds




            AM or PM         —         Displays AM or PM depending upon time of day

            A.M or P.M       —         Displays A.M or P.M depending upon time of day

            AD or BC          —         Displays AD or BC depending upon the date

            A.D or B.C        —         Displays AD or BC depending upon the date

            FM                    —         Prefix to month or day, suppresses padding of month or day

            TH                    —         Suffix to a number

            SP                    —         suffix to a number to be spelled out

            SPTH                —         Suffix combination of TH and SP to be both spelled out

            THSP                —         same as SPTH

Ex:




    SQL> select to_char(sysdate,’dd month yyyy hh:mi:ss am dy’) from dual;

TO_CHAR(SYSDATE,’DD MONTH YYYYHH:MI

—————————————————-

24 december  2006 02:03:23 pm sun     

    SQL> select to_char(sysdate,’dd month year’) from dual;

TO_CHAR(SYSDATE,’DDMONTHYEAR’)

——————————————————-

24 december  two thousand six

     SQL> select to_char(sysdate,’dd fmmonth year’) from dual;

TO_CHAR(SYSDATE,’DD FMMONTH YEAR’)

——————————————————-

24 december two thousand six

     SQL> select to_char(sysdate,’ddth DDTH’) from dual;

TO_CHAR(S

————

24th 24TH

     SQL> select to_char(sysdate,’ddspth DDSPTH’) from dual

TO_CHAR(SYSDATE,’DDSPTHDDSPTH

——————————————

twenty-fourth TWENTY-FOURTH

     SQL> select to_char(sysdate,’ddsp Ddsp DDSP ‘) from dual;

 




TO_CHAR(SYSDATE,’DDSPDDSPDDSP’)

————————————————

twenty-four Twenty-Four TWENTY-FOUR

  1. i) TO_DATE

    This will be used to convert the string into data format.

    Syntax: to_date (date)

    Ex:

         SQL> select to_char(to_date(’24/dec/2006′,’dd/mon/yyyy’), ‘dd * month * day’) from

                 dual;

TO_CHAR(TO_DATE(’24/DEC/20

————————–

24 * december  * Sunday

 

— If you are not using to_char oracle will display output in default date format.

  1. j) ADD_MONTH

    This will add the specified months to the given date

    Syntax: add_months (date, no_of_months)

    Ex:

          SQL> select add_months(to_date(’11-jan-1990′,’dd-mon-yyyy’), 5) from dual;

ADD_MONTHS

—————-

11-JUN-90

SQL> select add_months(to_date(’11-jan-1990′,’dd-mon-yyyy’), -5) from dual;

ADD_MONTH

—————

11-AUG-89          

  • If no_of_months is zero then it will display the same date.
  • If no_of_months is null then it will display nothing.




  1. k) MONTHS_BETWEEN

    This will give difference of months between two dates.

    Syntax: months_between (date1, date2)

    Ex:

         SQL> select months_between(to_date(’11-aug-1990′,’dd-mon-yyyy’), to_date(’11-jan-

                 1990′,’dd-mon-yyyy’)) from dual;

MONTHS_BETWEEN(TO_DATE(’11-AUG-1990′,’DD-MON-YYYY’),TO_DATE(’11-JAN-1990′,’DD-MON-YYYY’))

———————————————————————————————–

                                                                                        7

           SQL> select months_between(to_date(’11-jan-1990′,’dd-mon-yyyy’), to_date(’11-aug-

                 1990′,’dd-mon-yyyy’)) from dual;

 

MONTHS_BETWEEN(TO_DATE(’11-JAN-1990′,’DD-MON-YYYY’),TO_DATE(’11-AUG-1990′,’DD-MON-YYYY’))

————————————————————————————————-

                                                                                       -7

  1. l) NEXT_DAY

    This will produce next day of the given day from the specified date.

    Syntax: next_day (date,  day)

    Ex:

         SQL> select next_day(to_date(’24-dec-2006′,’dd-mon-yyyy’),’sun’) from dual;




NEXT_DAY(

————-

31-DEC-06

— If the day parameter is null then it will display nothing.

  1. m) LAST_DAY

    This will produce last day of the given date

    Syntax: last_day (date)

    Ex:

         SQL> select last_day(to_date(’24-dec-2006′,’dd-mon-yyyy’),’sun’) from dual;

LAST_DAY(

————-

31-DEC-06

  1. n) EXTRACT

    This is used to extract a portion of the date value.

    Syntax: extract ((year | month | day | hour | minute | second), date)

    Ex:

         SQL> select extract(year from sysdate) from dual;

EXTRACT(YEARFROMSYSDATE)

————————————

                    2006

 

— You can extract only one value at a time.

 

  1. o) GREATEST

 

     This will give the greatest date.

 

     Syntax: greatest (date1, date2, date3 … daten)

 

     Ex:

         SQL> select greatest(to_date(’11-jan-90′,’dd-mon-yy’),to_date(’11-mar-90′,’dd-mon-

                 yy’),to_date(’11-apr-90′,’dd-mon-yy’)) from dual;

 




  GREATEST(

  ————-

   11-APR-90

 

  1. p) LEAST

 

     This will give the least date.

 

     Syntax: least (date1, date2, date3 … daten)

 

     Ex:

         SQL> select least(to_date(’11-jan-90′,’dd-mon-yy’),to_date(’11-mar-90′,’dd-mon-

                 yy’),to_date(’11-apr-90′,’dd-mon-yy’)) from dual;

 

  LEAST(

  ————-

   11-JAN-90

  1. q) ROUND

    Round will rounds the date to which it was equal to or greater than the given date.

    Syntax: round (date, (day | month | year))

    If the second parameter was year then round will checks the month of the given date in the

    following ranges.

           

JAN      —          JUN     

            JUL       —          DEC

 




    If the month falls between JAN and JUN then it returns the first day of the current year.

    If the month falls between JUL and DEC then it returns the first day of the next year.

 

    If the second parameter was month then round will checks the day of the given date in the

    following ranges.

 

            1          —         15       

            16        —         31

 

    If the day falls between 1 and 15 then it returns the first day of the current month.

    If the day falls between 16 and 31 then it returns the first day of the next month.

 

    If the second parameter was day then round will checks the week day of the given date in   

    the following ranges.

 

            SUN      —          WED

            THU      —          SUN

    If the week day falls between SUN and WED then it returns the previous sunday.

    If the weekday falls between THU and SUN then it returns the next sunday.

 

  • If the second parameter was null then it returns nothing.
  • If the you are not specifying the second parameter then round will resets the time to the

     begining of the current day in case of user specified date.

  • If the you are not specifying the second parameter then round will resets the time to the

     begining of the next day in case of sysdate.

  




    Ex:

         SQL> select round(to_date(’24-dec-04′,’dd-mon-yy’),’year’), round(to_date(’11-mar-

                 06′,’dd-mon-yy’),’year’) from dual;

 

ROUND(TO_ ROUND(TO_

————   —————

01-JAN-05   01-JAN-06

           SQL> select round(to_date(’11-jan-04′,’dd-mon-yy’),’month’), round(to_date(’18-jan-

                 04′,’dd-mon-yy’),’month’) from dual;  

 

ROUND(TO_ ROUND(TO_

————-  —————

01-JAN-04    01-FEB-04

 

           SQL> select round(to_date(’26-dec-06′,’dd-mon-yy’),’day’), round(to_date(’29-dec-

                 06′,’dd-mon-yy’),’day’) from dual;

  

ROUND(TO_ ROUND(TO_

————–  ————–

24-DEC-06     31-DEC-06

 

           SQL> select to_char(round(to_date(’24-dec-06′,’dd-mon-yy’)), ‘dd mon yyyy hh:mi:ss am’)

                 from dual;

 

TO_CHAR(ROUND(TO_DATE(‘

———————————

24 dec 2006 12:00:00 am

  1. r) TRUNC

 




    Trunc will chops off the date to which it was equal to or less than the given date.

 

    Syntax: trunc (date, (day | month | year))

 

  • If the second parameter was year then it always returns the first day of the current year.
  • If the second parameter was month then it always returns the first day of the current month.
  • If the second parameter was day then it always returns the previous sunday.
  • If the second parameter was null then it returns nothing.
  • If the you are not specifying the second parameter then trunk will resets the time to the

      begining of the current day.

 

    Ex:

         SQL> select trunc(to_date(’24-dec-04′,’dd-mon-yy’),’year’), trunc(to_date(’11-mar-

                 06′,’dd-mon-yy’),’year’) from dual;

 

TRUNC(TO_ TRUNC(TO_

————-  ————–

01-JAN-04    01-JAN-06

 

                     SQL> select trunc(to_date(’11-jan-04′,’dd-mon-yy’),’month’), trunc(to_date(’18-jan-

                         04′,’dd-mon-yy’),’month’) from dual;

 

TRUNC(TO_ TRUNC(TO_

————-  ————-

01-JAN-04    01-JAN-04

  

  SQL> select trunc(to_date(’26-dec-06′,’dd-mon-yy’),’day’), trunc(to_date(’29-dec-06′,’dd- 

         mon-yy’),’day’) from dual;

 

TRUNC(TO_ TRUNC(TO_

————-  ————–

24-DEC-06 24-DEC-06

         

          SQL> select to_char(trunc(to_date(’24-dec-06′,’dd-mon-yy’)), ‘dd mon yyyy hh:mi:ss am’)

                 from dual;

 




TO_CHAR(TRUNC(TO_DATE(‘

———————————

24 dec 2006 12:00:00 am

 

  1. s) NEW_TIME

 

     This will give the desired timezone’s date and time.

 

     Syntax: new_time (date, current_timezone, desired_timezone)

 

     Available timezones are as follows.

 

    TIMEZONES

 

                        AST/ADT         —         Atlantic standard/day light time

                        BST/BDT          —         Bering standard/day light time

                        CST/CDT          —         Central standard/day light time

                        EST/EDT          —         Eastern standard/day light time

                        GMT                —         Greenwich mean time

                        HST/HDT         —         Alaska-Hawaii standard/day light time

                        MST/MDT         —         Mountain standard/day light time

                        NST                 —          Newfoundland standard time

                        PST/PDT          —         Pacific standard/day light time

                        YST/YDT          —         Yukon standard/day light time

 




    Ex:

        SQL> select to_char(new_time(sysdate,’gmt’,’yst’),’dd mon yyyy hh:mi:ss am’) from dual;

 

TO_CHAR(NEW_TIME(SYSDAT

———————————–

24 dec 2006 02:51:20 pm

 

          SQL> select to_char(new_time(sysdate,’gmt’,’est’),’dd mon yyyy hh:mi:ss am’) from dual;

TO_CHAR(NEW_TIME(SYSDAT

———————–

24 dec 2006 06:51:26 pm

 

  1. t) COALESCE

 

    This will give the first non-null date.

 

    Syntax: coalesce (date1, date2, date3 … daten)

 

    Ex:

         SQL> select coalesce(’12-jan-90′,’13-jan-99′), coalesce(null,’12-jan-90′,’23-mar-98′,null)

                 from dual;

 

COALESCE( COALESCE(

————-  ————

12-jan-90     12-jan-90

 

MISCELLANEOUS FUNCTIONS

 

  • Uid
  • User
  • Vsize
  • Rank
  • Dense_rank

 

  1. a) UID

 

     This will returns the integer value corresponding to the user currently logged in.

 

     Ex:

          SQL> select uid from dual;

 

       UID

———-

       319

 

  1. b) USER

 

     This will returns the login’s user name.

 

     Ex:

           SQL> select user from dual;

 




USER

—————-

SAKETH

 

  1. c) VSIZE

 

     This will returns the number of bytes in the expression.

 

     Ex:

          SQL> select vsize(123), vsize(‘computer’), vsize(’12-jan-90′) from dual;

 

VSIZE(123) VSIZE(‘COMPUTER’) VSIZE(’12-JAN-90′)

————-  ———————–  ———————-

         3                         8                                  9

 

  1. d) RANK

 

     This will give the non-sequential ranking.

 

     Ex:

          SQL> select rownum,sal from (select sal from emp order by sal desc);

 

    ROWNUM    SAL

    ———- ———-

         1       5000

         2       3000

         3       3000

         4       2975

         5       2850

         6       2450

         7       1600

         8       1500

         9       1300

        10       1250

        11       1250

        12       1100

        13       1000

        14        950

        15        800

 




     SQL> select rank(2975) within group(order by sal desc) from emp;

 

RANK(2975)WITHINGROUP(ORDERBYSALDESC)

———————————————————

                                    4

  1. d) DENSE_RANK

 

     This will give the sequential ranking.

    

Ex:

     SQL> select dense_rank(2975) within group(order by sal desc) from emp;

 

DENSE_RANK(2975)WITHINGROUP(ORDERBYSALDESC)

—————————————————————–

                                          3

 

CONVERSION FUNCTIONS

 

  • Bin_to_num
  • Chartorowid
  • Rowidtochar
  • To_number
  • To_char
  • To_date




  1. a) BIN_TO_NUM

 

     This will convert the binary value to its numerical equivalent.

 

     Syntax: bin_to_num( binary_bits)

 

     Ex:

          SQL> select bin_to_num(1,1,0) from dual;

 

BIN_TO_NUM(1,1,0)

————————

                6

  • If all the bits are zero then it produces zero.
  • If all the bits are null then it produces an error.

 

  1. b) CHARTOROWID

 

     This will convert a character string to act like an internal oracle row identifier or rowid.

 

  1. c) ROWIDTOCHAR

 

    This will convert an internal oracle row identifier or rowid to character string.

 

  1. d) TO_NUMBER

 




    This will convert a char or varchar to number.

 

  1. e) TO_CHAR

 

    This will convert a number or date to character string.

  1. f) TO_DATE

    This will convert a number, char or varchar to a date.

GROUP FUNCTIONS

  • Sum
  • Avg
  • Max
  • Min
  • Count

Group functions will be applied on all the rows but produces single output.

  1. a) SUM

     This will give the sum of the values of the specified column.

     Syntax: sum (column)

     Ex:

          SQL> select sum(sal) from emp;

  SUM(SAL)

   ———-

     38600

 

  1. b) AVG

 

     This will give the average of the values of the specified column.

 

     Syntax: avg (column)

 

     Ex:

          SQL> select avg(sal) from emp;

 

   AVG(SAL)

   —————

   2757.14286

 

  1. c) MAX

     This will give the maximum of the values of the specified column.

     Syntax: max (column)

 




     Ex:

          SQL> select max(sal) from emp;

 

    MAX(SAL)

   ———-

     5000

  1. d) MIN

     This will give the minimum of the values of the specified column.

     Syntax: min (column)

     Ex:

          SQL> select min(sal) from emp

   MIN(SAL)

   ———-

     500

  1. e) COUNT

     This will give the count of the values of the specified column.

     Syntax: count (column)

     Ex:

          SQL> select count(sal),count(*) from emp;

COUNT(SAL)   COUNT(*)

————–    ————

        14                     14




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Oracle SQL Tutorial Study Material SQL Queries Interview Questions and Answers Freshers and Experienced with examples




Oracle SQL Tutorial Study Material SQL Queries Interview Questions and Answers Freshers and Experienced with examples

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