Date Functions

In previous posts,we learnt about Numeric Functions 
and String Functions ,Now lets check out Date Functions in SQL.

DATE FUNCTIONS

a)    Sysdate
b)    Current_date
c)    Current_timestamp
d)    Systimestamp
e)    Localtimestamp
f)    Dbtimezone
g)    Sessiontimezone
h)    To_char
i)    To_date
j)    Add_months
k)    Months_between
l)    Next_day
m)    Last_day
n)    Extract
o)    Greatest
p)    Least
q)    Round
r)    Trunc
s)    New_time
t)    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.

a) SYSDATE

     This will give the current date and time.
      Ex:    SQL> select sysdate from dual;

SYSDATE
-----------
24-DEC-06

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

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

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

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

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 

g) SESSIONTIMEZONE

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

    Ex:    SQL> select sessiontimezone from dual;

SESSIONTIMEZONE
------------------------------------
+05:30

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


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.
   
j) ADD_MONTHS

    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          

1)    If no_of_months is zero then it will display the same date.
2)    If no_of_months is null then it will display nothing.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

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.

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')) from dual;
LAST_DAY(
-------------
31-DEC-06

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.

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

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

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

    1) If the month falls between JAN and JUN then it returns the first day of the current year.
    2) If the month falls between JUL and DEC then it returns the first day of the next year.

    3) 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.

1)    If the second parameter was null then it returns nothing.
2)    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. 
3)    If the you are not specifying the second parameter then round will resets the time to the the time to the ining 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
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))

1)    If the second parameter was year then it always returns the first day of the current year.
2)    If the second parameter was month then it always returns the first day of the current month.
3)    If the second parameter was day then it always returns the previous sunday.
4)    If the second parameter was null then it returns nothing.
5)    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

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

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

String Functions

In Our Previous post,we learnt about Numeric Functions and now lets learn about string functions.


STRING FUNCTIONS 
 We have following types of string functions in SQL.

a)    Initcap
b)    Upper
c)    Lower
d)    Length
e)    Rpad
f)    Lpad
g)    Ltrim
h)    Rtrim
i)    Trim
j)    Translate
k)    Replace
l)    Concat  ( ‘ || ‘ Concatenation operator)
m)    Ascii
n)    Chr
o)    Substr
p)    Instr
q)    Decode
r)    Greatest
s)    Least
t)    Coalesce

a) INITCAP

     This will capitalize the initial letter of the string.

     Syntax: initcap (string)

     Ex:    SQL> select initcap('computer') from dual;

INITCAP
-----------
Computer

b) UPPER

     This will convert the string into uppercase.

     Syntax: upper (string)

     Ex:     SQL> select upper('computer') from dual;
UPPER
--------
COMPUTER

c) LOWER

     This will convert the string into lowercase.

     Syntax: lower (string)

     Ex:    SQL> select lower('COMPUTER') from dual;

LOWER
---------
computer

d) LENGTH:-     
       This will give length of the string.

     Syntax: length (string)

     Ex:     SQL> select length('computer') from dual;

LENGTH
----------
       8

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.


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.

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.

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.

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

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

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


l) 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

m) 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

n) 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

o) 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

 1)If no_of_chars parameter is negative then it will display nothing.

 2)If both parameters except string are null or zeros then it will display nothing.

 3)If no_of_chars parameter is greater than the length of the string then it ignores and calculates based on the original string length.

 4)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
p) 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
1) If you are not specifying start_chr_count and occurrence then it will start search from the beginning and finds first occurrence only. 
2) If both parameters start_chr_count and occurrence are null, it will display nothing.

q) 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
1) If the number of parameters are odd and different then decode will display nothing.
2) If the number of parameters are even and different then decode will display last value.
3) If all the parameters are null then decode will display nothing.                                                        
4) If all the parameters are zeros then decode will display zero.

r) GREATEST

     This will give the greatest string.

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

     Ex:      SQL> select greatest('a', 'b', 'c'), greatest('satish','srinu','Ram') from dual;


GREAT GREAT
-------  -------
    c        srinu

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

s) LEAST

    This will give the least string.

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

    Ex:     SQL> select least('a', 'b', 'c'), least('satish','srinu','Ram') from dual;

LEAST LEAST
-------  -------
    a        Ram

1)If all the parameters are nulls then it will display nothing.                                                        
2) If any of the parameters is null it will display nothing.
  
t) COALESCE

    This will gives the first not-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
 

Numeric Functions

In SQL,We have different types of functions,lets learn those now.

1.1 SQL Functions

In This post,lets learn about Numeric Functions:

NUMERIC FUNCTIONS:-
a)    Abs
b)    Sign
c)    Sqrt
d)    Mod
e)    Nvl
f)    Power
g)    Exp
h)    Ln
i)    Log
j)    Ceil
k)    Floor
l)    Round
m)    Trunk
n)    Bitand
o)    Greatest
p)    Least
q)    Coalesce

In This diagram,i ill show only important numeric functions which are only useful for our real time scenarios.

 




                                                                             
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
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


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

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

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

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                           

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

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

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

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
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
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
     

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

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

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   

1) If all the values are zeros then it will display zero.

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

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

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

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
 

How to Do Multi Insert In SQL

MULTI TABLE INSERTS

We have table called DEPT with the following columns and data

DEPTNO DNAME LOC
--------           --------            ----
10 accounting new york
20 research dallas
30 sales Chicago
40 operations boston

a) CREATE STUDENT TABLE

     SQL> Create table student(no number(2),name varchar(2),marks number(3));

b) MULTI INSERT WITH ALL FIELDS
     SQL> Insert all
             Into student values(1,’a’,100)
             Into student values(2,’b’,200)
             Into student values(3,’c’,300)
             Select *from dept where deptno=10;

     -- This inserts 3 rows
c) MULTI INSERT WITH SPECIFIED FIELDS
     SQL> insert all
             Into student (no,name) values(4,’d’)
             Into student(name,marks) values(’e’,400)
             Into student values(3,’c’,300)
             Select *from dept where deptno=10;

     -- This inserts 3 rows

d) MULTI INSERT WITH DUPLICATE ROWS

     SQL> insert all
             Into student values(1,’a’,100)
             Into student values(2,’b’,200)
             Into student values(3,’c’,300)
             Select *from dept where deptno > 10;

     -- This inserts 9 rows because in the select statement retrieves 3 records (3 inserts for 
         each row retrieved)

e) MULTI INSERT WITH CONDITIONS BASED

     SQL> Insert all
             When deptno > 10 then
             Into student1 values(1,’a’,100)
             When dname = ‘SALES’ then
             Into student2 values(2,’b’,200)
             When loc = ‘NEW YORK’ then
             Into student3 values(3,’c’,300)
             Select *from dept where deptno>10;

     -- This  inserts 4 rows because the first condition satisfied 3 times, second condition  
         satisfied once and the last none.

f) MULTI INSERT WITH CONDITIONS BASED AND ELSE

    SQL> Insert all
            When deptno > 100 then
            Into student1 values(1,’a’,100)
            When dname = ‘S’ then
            Into student2 values(2,’b’,200)
            When loc = ‘NEW YORK’ then
            Into student3 values(3,’c’,300)
            Else 
            Into student values(4,’d’,400)
            Select *from dept where deptno>10;

     -- This inserts 3 records because the else satisfied 3 times

g) MULTI INSERT WITH CONDITIONS BASED AND FIRST

     SQL> Insert first
             When deptno = 20 then
             Into student1 values(1,’a’,100)
             When dname = ‘RESEARCH’ then
             Into student2 values(2,’b’,200)
             When loc = ‘NEW YORK’ then
             Into student3 values(3,’c’,300)
             Select *from dept where deptno=20;
     
     -- This inserts 1 record because the first clause avoid to check the remaining 
         conditions once the condition is satisfied.

h) MULTI INSERT WITH CONDITIONS BASED, FIRST AND ELSE

     SQL> Insert first
             When deptno = 30 then
              Into student1 values(1,’a’,100)
              When dname = ‘R’ then
              Into student2 values(2,’b’,200)
              When loc = ‘NEW YORK’ then
              Into student3 values(3,’c’,300)
              Else
              Into student values(4,’d’,400)
              Select *from dept where deptno=20;

     -- This inserts 1 record because the else clause satisfied once 

i) MULTI INSERT WITH MULTI TABLE TABLES

    SQL> Insert all
            Into student1 values(1,’a’,100)
            Into student2 values(2,’b’,200)
            Into student3 values(3,’c’,300)
            Select *from dept where deptno=10;

    -- This inserts 3 rows

Create table with existed table

In earlier post, we have checked about Aliases in SQL and now lets see creating table with existed table.

CREATE TABLE USING EXISTED TABLE WITH SELECT STATEMENT:
We can create a table using existing table [along with data].

Syntax:   Create table <new_table_name> [col1, col2, col3 ... coln] as select * from 
                                                               <old_table_name>;

Ex:    SQL> create table student1 as select * from student;
    
    Creating table with your own column names.
    SQL> create table student2 (sno, sname, smarks) as select * from student;
    
    Creating table with specified columns.
    SQL> create table student3 as select no,name from student;

    Creating table with out table data.
    SQL> create table student2(sno, sname, smarks) as select * from student where 1 = 2;

    In the above where clause give any condition which does not satisfy.Instead of where 1=2 if you specify where 1=1 then condition got satisfied so it ill create table with data.


INSERT INTO TABLE USING EXISTED TABLE WITH SELECT STATEMENT:

Using this we can insert existing table data to another table in a single trip. But the table structure should be same.

Syntax:     Insert into <table1> select * from <table2>;    

Ex:     SQL> insert into student1 select * from student;

     Inserting data into specified columns

     SQL> insert into student1(no, name) select no, name from student;

    

Table alias and Column alias

Table Alias: 
In General, We know that in police station, criminals will called with alias name eg : Shankar alias shankaranna.

It means some extra name,he is having.Similar to that table also can have another name.

Let's see some example:

SQL > Select * from emp e;

here "e" is alias for emp table. you can specify any alias name but make it simple alias name.

Similar to table alias, we have column alias also in Oracle SQL.

Eg: 

SQL> Select ename EMPLOYEE_NAME FROM EMP;

here EMPLOYEE_NAME is alias for ename column.

Lets see mixed alias combination.

 SQL> Select E.ename EMPLOYEE_NAME,e.sal SALARY FROM EMP e;

 If you are mentioning alias name then it would be better practice to use alias name with dot following column name(eg: e.ename ) for simple query also.