The WHERE clause is used to filter MySQL query results based on conditions and include rows that meet the conditions in the results. It performs conditional filtering by specifying expressions, such as value comparison, range comparison, or logical operations, and supports complex queries and acquisition of specific data.
The role of the WHERE clause in MySQL
The WHERE clause is used in MySQL query statements to filter the returned results a powerful tool. It allows you to specify specific rows to be included in the query results.
Function
The main function of the WHERE clause is to filter data from the table based on specified conditions.
Syntax
<code>SELECT column_list FROM table_name WHERE condition;</code>
Where:
condition
is the expression used to filter rows. condition
can be:
column_name = value
)column_name BETWEEN value1 AND value2
) AND
, OR
, NOT
)Usage
The WHERE clause is usually used for:
Example
<code>-- 获取所有名为 "John" 的客户 SELECT * FROM customers WHERE name = "John";</code>
<code>-- 获取订单总额大于 500 的所有订单 SELECT * FROM orders WHERE total_amount > 500;</code>
Notes
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