经常使用的sql语句

1：查询euc_job_dict 表的id，name,重名name的记录条数，按name分组，且重名数>50条的数据，按数量降序排列

SELECT id,NAME,COUNT(NAME) AS co FROM euc_job_dict GROUP BY NAME HAVING co>50  ORDER BY co DESC;

2:连表查询：
SELECT * FROM erp_dept AS er LEFT JOIN erp_hr AS eh ON er.bh=eh.bh WHERE eh.deleted IS NULL;

3：模糊匹配 like
select * from erp_dept wher name like "%集团%"

4：关键词：IN 查找在某范围内的全部记录
select * from tableA where classid in (select classid from tableb where projid="xxx");

5:删除数据库中表的某些相同的某些记录

delete from tablename where only_Id not in(select min(only_id) from tablename group by sameName)
或者
delete from tablename where only_Id in (select only_id from tableaa group by only_id where count(only_id)>1)