WHERE conditions
Sometimes when operating the database, only some conditional data is operated. In this case, a WHERE clause can be added to the SQL statement to specify the conditions for data operation.
Syntax:
SELECT column,… FROM tb_name WHERE definition
The WHERE keyword is followed by a valid expression (definition), which represents the conditions that the operated data record must meet.
Except SELECT, the WHERE condition keyword can be used in any situation allowed by SQL syntax, such as UPDATE (update), DELETE (delete), etc.
Example:
SELECT * FROM user WHERE username = 'Jack'
This example specifies the query condition for data where username is equal to Jack.
Operator description in WHERE expression:
Parameter description:
Some WHERE examples
According to user name Query the specified user:
SELECT * FROM user WHERE username = 'Jack'
Query the user names and ID numbers registered after 0:00 a.m. on January 1, 2009:
$regdate = mktime(00, 00, 01, 01, 01, 2009); SELECT uid,username FROM user WHERE regdate >= $regdate
Search for all users whose user names contain the word user:
SELECT * FROM user WHERE username LIKE '%user%'
Search for all users whose user names contain user or admin:
SELECT * FROM user WHERE username LIKE '%user%' OR username LIKE '%admin%'
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