mysql 常用数据查询

1.关联查询修改UPDATE  ex_question_questioncategory t5 INNER JOIN (SELECT qc.QUESTION_ID,qc.QUESTION_CATEGORY_ID FROM ex_question_questioncategory qc RIGHT JOIN (SELECT q.QUESTION_ID,q.CONTENT from ex_question q WHERE q.CONTENT LIKE ‘%关键字%‘) t1 ON qc.QUESTION_ID =t1.QUESTION_ID ) t2ON t5.QUESTION_ID=t2.QUESTION_IDSET t5.QUESTION_CATEGORY_ID=‘f39d2a3e49c0b98f0149c1f4cd9f0022‘2.-- 查询A表中存在而B表中不存在的数据（A：domain，B：resource中有个外键）select a.* from sys_domain a where not EXISTS (select b.DOMAIN_FK from sys_resource b where a.DOMAIN_ID=b.DOMAIN_FK)