How does the WHERE clause filter rows in a query?
Understanding the WHERE Clause in MySQL
In MySQL, the WHERE clause is used to filter rows returned by a query based on specified conditions. Only the rows that meet the condition(s) defined in the WHERE clause are included in the result set.
Key Features of the WHERE Clause
Filters rows using comparison operators like
=,>,<,>=,<=,<>.Supports logical operators such as
AND,OR, andNOTto combine multiple conditions.Can use pattern matching with
LIKEand regular expressions withREGEXP.Handles NULL values using
IS NULLorIS NOT NULL.Can include subqueries to filter based on results from other tables.
The WHERE clause is applied before grouping (GROUP BY) or ordering (ORDER BY) takes place, ensuring that only the relevant rows are processed further in the query.
Example of WHERE Clause Usage