常用SQL

 

查询及删除重复记录的SQL语句

1、查找表中多余的重复记录，重复记录是根据单个字段（Id）来判断

select * from 表 where Id in (select Id from 表 group byId having count(Id) > 1)

2、删除表中多余的重复记录，重复记录是根据单个字段（Id）来判断，只留有rowid最小的记录

DELETE from 表 WHERE (id) IN ( SELECT id FROM 表 GROUP BY id HAVING COUNT(id) > 1) AND ROWID NOT IN (SELECT MIN(ROWID) FROM 表 GROUP BY id HAVING COUNT(*) > 1);

3、查找表中多余的重复记录（多个字段）

select * from 表 a where (a.Id,a.seq) in(select Id,seq from 表 group by Id,seq having count(*) > 1)

4、删除表中多余的重复记录（多个字段），只留有rowid最小的记录

delete from 表 a where (a.Id,a.seq) in (select Id,seq from 表 group by Id,seq having count(*) > 1) and rowid not in (select min(rowid) from 表 group by Id,seq having count(*)>1)

5、查找表中多余的重复记录（多个字段），不包含rowid最小的记录

select * from 表 a where (a.Id,a.seq) in (select Id,seq from 表 group by Id,seq having count(*) > 1) and rowid not in (select min(rowid) from 表 group by Id,seq having count(*)>1)

 6、计算两个日期之间的天数

SELECT ABS(TO_DATE('2014-12-31','yyyy-MM-dd')-TO_DATE('2014-01-01','yyyy-MM-dd'))+1 AS AMOUNT FROM dual

 7、得到两个日期之间的所有日期

SELECT to_date('2014-01-01', 'yyyy-mm-dd') + rownum - 1 AS sdate
		            FROM dual
		          CONNECT BY rownum <= trunc(to_date('2014-12-31', 'yyyy-mm-dd')) -
		                     to_date('2014-01-01', 'yyyy-mm-dd') + 1

 8、查找父节点下的所有子节点

SELECT * FROM sys_menu
   START WITH ID = 'ZZZZZZZZZZZZZZZZ'
   CONNECT BY NOCYCLE PRIOR ID = MENU_PARENT_ID

 9、查找子节点的所有父节点

SELECT * FROM sys_menu
   START WITH ID = 'ZZZZZZZZZZZZZZZZ'
   CONNECT BY NOCYCLE PRIOR MENU_PARENT_ID = ID