由于锁定实现问题，
MySQL不允许使用
DELETe或引用受影响的表
UPDATE。
您需要在
JOIN此处制作一个：
DELETE gc.*FROM guide_category AS gc LEFT JOIN guide AS g ON g.id_guide = gc.id_guideWHERe g.title IS NULL
或只是使用
NOT IN：
DELETe FROM guide_category AS gc WHERe id_guide NOT IN ( SELECt id_guide FROM guide )
