Filtering Data in SQL Server Queries

Using the WHERE Clause

The WHERE clause is used in SQL Server SELECT statements to specify conditions that filter which rows are returned.

It comes after the FROM clause and before clauses like ORDER BY or GROUP BY.

• Syntax: SELECT columns FROM table WHERE condition;
• Only rows satisfying the condition appear in the result set.

Comparison Operators

Comparison operators allow you to compare column values to constants or other columns.

Common operators include equals, not equals, greater than, less than, and their variations.

• = (equal to)
• <> or != (not equal to)
• > (greater than)
• < (less than)
• >= (greater than or equal to)
• <= (less than or equal to)

Logical Operators for Multiple Conditions

Logical operators combine multiple conditions in the WHERE clause to refine filtering.

They help create complex queries that match multiple criteria.

• AND - all conditions must be true
• OR - at least one condition must be true
• NOT - negates a condition

Examples of Filtering Data

Let's look at practical examples demonstrating filtering with WHERE, comparison, and logical operators.