MySQL UPDATE查询与子查询永远在一起

避免子查询，请使用联接：

UPDATe table2LEFT JOIN table1 ON (table2.id = table1.id)SET table2.id_occurrences = COUNT(table1.id)GROUP BY table2.id

哦，UPDATE不支持GROUP BY。试试这个查询：

UPDATE table2LEFT JOIN (   SELECT id, COUNT(*) AS cnt FROM table1 GROUP BY id) AS t1ON (table2.id = t1.id)SET table2.id_occurrences = t1.cnt