Functions:
- Function can return an only single row or a table.
- It is a set of SQL statements that only accept input parameters, perform Task and then return the result.
Two types of Functions:
1. Built
in Functions
2. User
defined functions
Built in Functions:
· These
functions are defined by the SQL SERVER for different purpose.
Types:
1.
Scalar OR single row function
2.
Aggregate functions or group function
Before
going to the function we just know the oracle Created table DUAL:
· DUAL
is a table automatically created by oracle along with the data dictionary. DUAL
is the schema of the users SYS, but it is accessible by the all users and the
name of dual.
· It
has one DUMMY column defined to be varchar2(1) and contains one row with a
value ‘X’
· Dual
table is useful for computing constant expression with the SELECT statement.
Desc DUAL;
Select * from dual;
Scalar functions:
Function |
Description |
Example |
Output |
Abs(n) |
It
returns absolute values |
Select
abs(-100) from dual; |
100 |
Floor(n) |
It
returns largest integer equal to or less than n |
Select
floor(32.75) from dual; |
32 |
Ceil(n) |
It
returns largest integer equal to or greater than n |
Select
ceil(32.75) from dual; |
33 |
Exp(n) |
E
to the power of n |
Select
exp(4) from dual; |
54.598150033144236 |
Ln(n) |
It
returns log value of n |
Select
ln(2) from dual; |
0.693147185599453 |
Mod(m,n) |
It
returns remainder |
Select
mod(10,3) from dual; |
1 |
Power(m,n) |
It
returns m to the power of n |
Select
power(4,2) from dual; |
16 |
Round(n,[m]) |
It
returns round of the particular value |
Select
round(135.375, 2) from dual; |
135.38 |
Sign(n) |
It returns a value of -1 for negative expressions and +1 for positive expressions |
Select
sign(-20.5) from dual; |
-1 |
Sqrt(n) |
Square
root of n |
Select
sqrt(4) from dual; |
2 |
Trunc(n,[m]) |
It
returns n truncated to m decimal places |
Select
trunc(10.37, 3)from dual; |
10.370 |
Character functions:
Function |
Description |
Example |
ASCII(char) |
It
returns ASCII value of the character |
Select
Ascii(Ename) from emp; |
INSTR( string1,string2) |
It
returns position of a substring in a string |
Select
Instr(‘Sql’,’q’) |
Length(string) |
It
returns the length of the string in bytes |
Select Length(‘date’) from dual; |
Lower(string) |
It
converts string to lower case |
Select
Lower(‘SQL’) from dual; |
Upper(string) |
It
converts string to upper case |
Select
Upper(‘sql’) from dual; |
Lpad(string,length,lpad_string) |
Left
pads a string with another ,to a certain length |
Select Lpad(ename,20,’emp’) from emp; |
Rpad(string,length,rpad_string) |
Right
pads a string with another ,to a certain length |
Select Rpad(ename,20,’emp’) from emp; |
Ltrim(string) |
Removes leading spaces from a string. |
Select Ltrim(‘ SQL‘) from dual; |
Rtrim(string) |
Removes trailing spaces from a string. |
Select Rtrim(‘SQL ‘) from dual; |
Replace(string,from_string,
new_string) |
Replaces
all occurrences of the sub string with in a string, with a new string |
Select Replace(‘xyz_yz’,’x’,’z’)From dual; |
Substr(string,
start, length) |
It
extract a sub string from a string and starting with any position |
Select Substr(ename,2,6)From emp; |
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