Accessing Query Results as User Variables in MySQL
Setting user variables based on query results is feasible in MySQL, alleviating the need for nested queries.
Approach:
To accomplish this, incorporate the variable assignment within the query itself:
<code class="mysql">SET @user := 123456; SELECT @group := `group` FROM user WHERE user = @user; SELECT * FROM user WHERE `group` = @group;</code>
Example:
Consider a table named "user" with columns "user" and "group":
<code class="mysql">CREATE TABLE user (`user` int, `group` int); INSERT INTO user VALUES (123456, 5); INSERT INTO user VALUES (111111, 5);</code>
Query:
<code class="mysql">SET @user := 123456; SELECT @group := `group` FROM user WHERE user = @user; SELECT * FROM user WHERE `group` = @group;</code>
Output:
<code class="mysql">+--------+-------+ | user | group | +--------+-------+ | 123456 | 5 | | 111111 | 5 | +--------+-------+ 2 rows in set (0.00 sec)</code>
Alternate Approach:
An alternative method is to use "LIMIT 1" within a subquery:
<code class="mysql">SET @user := 123456; SELECT `group` FROM user LIMIT 1 INTO @group; SELECT * FROM user WHERE `group` = @group;</code>
Remember to use := as the assignment operator in SET statements. Non-SET statements require := for assignment, while = is treated as a comparison operator.
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