mysql - 在mysql上连接两个表

Question

所以目前我在两个 mysql tabales 之间有关系： wp_bp_activity与“id”和“content”和 wp_bp_activity_meta与“activity_id”这将匹配 wp_bp_activity id 和“meta_value”我试图根据 wp_bp_activity_meta -> meta_value 的文本输出wp_bp_activity -> content where wp_bp_activity -> id = wp_bp_activity_meta -> activity_id 甚至不确定这样的事情是否可行。我被困住了！这是我到目前为止的代码：

$query = "SELECT * FROM wp_bp_activity_meta WHERE meta_value LIKE 'test'";

Answer 1

SELECT  a.*, b.*
FROM    wp_bp_activity a
        INNER JOIN wp_bp_activity_meta b
            ON CONCAT(a.id, a.meta_value) = b.activity_id

Answer 2

$query = "SELECT *
FROM wp_bp_activity_meta
INNER JOIN wp_bp_activity
ON wp_bp_activity.if = wp_bp_activity_meta.activity_id
WHERE meta_value LIKE 'test' ";