Sunday, September 25, 2011

SQL Tutorial Part4

SQL – Operators

What is an Operator in SQL?

An operator is a reserved word or a character used primarily in an SQL statement's WHERE clause to perform operation(s), such as comparisons and arithmetic operations. Operators are used to specify conditions in an SQL statement and to serve as conjunctions for multiple conditions in a statement.

       Arithmetic operators
       Comparison operators
       Logical operators
       Operators used to negate conditions


SQL Arithmetic Operators:

Assume variable a holds 10 and variable b holds 20 then:

Show Examples
Operator                   Description                                    Example

+            Addition - Adds values on either side of       a + b will give 30
             the operator

-            Subtraction - Subtracts right hand                  a - b will give -10
             operand from left hand operand

*            Multiplication - Multiplies values on either    a * b will give 200
             side of the operator

/            Division - Divides left hand operand by         b / a will give 2
             right hand operand

%            Modulus - Divides left hand operand by     b % a will give 0
             right hand operand and returns
             remainder

SQL Comparison Operators:

Assume variable a holds 10 and variable b holds 20 then:

Show Examples

Operator              Description                                      Example

=            Checks if the value of two operands are        (a = b) is not true.
             equal or not, if yes then condition
             becomes true.

!=          Checks if the value of two operands are         (a != b) is true.
             equal or not, if values are not equal then
             condition becomes true.

<>          Checks if the value of two operands are        (a <> b) is true.
             equal or not, if values are not equal then
             condition becomes true.

>           Checks if the value of left operand is               (a > b) is not true.
             greater than the value of right operand,
             if yes then condition becomes true.

<            Checks if the value of left operand is less         (a < b) is true.
             than the value of right operand, if yes
             then condition becomes true.

>=          Checks if the value of left operand is               ( a >= b) is not true.
             greater than or equal to the value of
             right operand, if yes then condition
             becomes true.

<=          Checks if the value of left operand is less         (a <= b) is true.
             than or equal to the value of right
             operand, if yes then condition becomes
             true.

!<           Checks if the value of left operand is not          (a !< b) is false.
             less than the value of right operand, if
             yes then condition becomes true.

!>           Checks if the value of left operand is not           (a !> b) is true.
             greater than the value of right operand,
             if yes then condition becomes true.

SQL Logical Operators:

Here is a list of all the logical operators available in SQL.

Show Examples  
 Operator                                            Description

ALL                         The ALL operator is used to compare a value to all values in another
                                 valueset.

AND                       The AND operator allows the existence of multiple conditions in an SQL
                                statement's WHERE clause.

ANY                       The ANY operator is used to compare a value to any applicable value in
                                the list according to the condition. 
 
BETWEEN             The BETWEEN operator is used to search for values that are within a set
                                of  values, given the minimum value and the maximum value.

EXISTS                  The EXISTS operator is used to search for the presence of a row in a
                               specified table that meets certain criteria.

IN                           The IN operator is used to compare a value to a list of literal values that
                                have been specified.

LIKE                      The LIKE operator is used to compare a value to similar values using
                               wildcard operators.

NOT                       The NOT operator reverses the meaning of the logical operator with
                                which it is used. NOT EXISTS, NOT BETWEEN, NOT IN etc

OR                          The OR operator is used to combine multiple conditions in an SQL
                                 statement's WHERE clause.

IS NULL                The NULL operator is used to compare a value with a NULL value.

UNIQUE                The UNIQUE operator searches every row of a specified table for
                               uniqueness (  no duplicates).