Logical and Comparison Operators

tags: #sql

Logical Operators

What is a logical operator?

SQL logical operators are used to combine and evaluate multiple conditions in a query's WHERE or HAVING clauses. The logical operators include:

1. AND: returns true if all conditions are true

SELECT Column1, column2, ...
FROM table_name
WHERE condition1 AND condition2 AND ...

2. OR: returns true if any of the conditions are true

SELECT Column1, column2, ...
FROM table_name
WHERE condition1 OR condition2 OR ...

3. NOT: negates the truth value of a condition

SELECT Column1, column2, ...
FROM table_name
WHERE NOT condition1

These operators can be used to construct complex conditions in a query to filter data based on multiple criteria.

Comparison Operators

What are comparison operators?

Comparison operators are used to compare two values and return a boolean (TRUE or FALSE) result.

List of comparison operators

1. Equality

VALUE = VALUE2

2. Not Equal to

VALUE <> VALUE2

// alternative
VALUE != VALUE2

3. Less or Greater than

VALUE > VALUE2 // greater than

VALUE < VALUE2 // less than

VALUE >= VALUE2 // greater than or equal to

VALUE <= VALUE2 // less than or equal to

4. Between range of values

SELECT column1, column2, ...
FROM table_name
WHERE column_name BETWEEN (value1 AND value2);

5. Like (pattern matching)

SELECT column1, column2, ...
FROM table_name
WHERE column_name LIKE pattern;

• See also: Wildcard Matching (Pattern Matching)

6. To compare a value to some SET object (e.g., list) using IN

SELECT column1, column2, ...
FROM table_name
WHERE column_name IN (value1, value2, ...);