qq_30629571的博客

a表字段有user_id,status,heart_time三个字段 b代表临时数据表，将要比较的值作为b的user_id参数, ON (a.user_id = b.user_id)是比较，后面两句话是两条选择 MERGE INTO 表名 a USING ( SELECT 参数值 as user_id FROM dual ) b ON (a.user_id = b.user_id) WHEN...