Category: ASE: T-SQL: Logical Operators

Logical Operators

A logical operator is part of a Query, i.e. an enquiry on a database. Logical operators are used to compare logical expressions. For example, to check if two expressions are equal or not. An exception to this are NULL values. With NULL-values the result of logical operations can be unknown.

Logical Operators and examples

= (equal)

select * from your_table

      where a = b

<> (not equal)

select * from your_table

      where a <> b

!= (not equal)

select * from your_table

      where a != b

> (greater than)

select * from your_table

      where a > b

>= (greater or equal)

select * from your_table

      where a >= b

< (less than)

select * from your_table

      where a < b

=< (less or equal)

select * from your_table

      where a =< b

!> (not greater than)

select * from your_table

      where a !> b

!< (not less than)

select * from your_table

      where a !< b

and (combines logical expressions)
```
if (@a > @b) and (@a != @d)
```
or (combines logical expressions)
```
if (@a > @b) or (@a != @d)
```
not (negates logical expressions)
```
if not(@a > @b)
```
[not] like
(see pattern matching operators)

[not] in

select * from your_table

      where a in (1, 5, 8)

The same result can be achieved using the query:

select * from your_table

      where a = 1 or a = 5 or a = 8

[not] between

select * from your_table

      where id between 100 and 150

*=
outer join operator
=*
outer join operator
exists
subquery operator
any
subquery operator
all
subquery operator
in
subquery operator