SQL语句练习

Posted 2020-12-24 南国叶子

查询21-30条的数据库

MySql查询

select * from table LIMIT 20,10

SqlServer查询

2.1先根据ID升序 查询前30条记录信息，再将查询的结果根据ID降序 查询前20条记录

Select * from （select top 20 * from （select top 30 * from 表名 order by ID）t1 order by ID desc  )t2 order by ID

2.2先将查询出前10条记录信息，然后将这10条信息从结果集中剔除掉

select top 10 * from 表名 where id not in (select top 10 id from 表名 order by id asc ）order by ID

先查询出前10条记录最大的ID，然后再查询出>ID的前10条记录信息

select top 10 * from 表名 where ID >(select max(ID) from (select top 10 ID From 表名 order by ID) t1) order by ID

Oracle查询

select * from (select rownum no,* from 表名 where rownum <=30 )where no >20

 

如何删掉数据重复，仅仅保留一条数据

Delet from table t where (t.字段,t.字段2,...,t.字段n)in (SELECT 字段1,字段2,...，字段n from table group by 字段1,字段2,...，字段n having count(*)>1)and rowid not in(select min(rowid) from table group by 字段1,字段2,...，字段n having count(*)>1)