Having用法 分享

它主要用於分組後的條件過濾，未分組的用 where，若是用了group by 那麼後面的過濾條件就不能再用where了，要用having

Select COUNT(PartID) ,PartCode,PartCode2 From Base_Part   Group by PartCode,PartCode2  having count(PartID) >1

 

2.group by方法

查數據:
　　select count(num), max(name) from student --列出重複的記錄數，並列出他的name屬性
　　group by num
　　having count(num) >1 --按num分組後找出表中num列重複，即出現次數大於一次
刪數據：
　　delete from student
　　group by num
　　having count(num) >1
　　這樣的話就把全部重複的都刪除了。

3.用distinct方法 -對於小的表比較有用

create table table_new as   select distinct *   from table1 minux
truncate table table1;
insert into table1 select * from table_new;

查詢及刪除重複記錄的方法大全 一、查找表中多餘的重複記錄，重複記錄是根據單個字段（peopleId）來判斷select * from people where peopleId in (select  peopleId  from  people  group  by  peopleId  having  count(peopleId) > 1) 二、刪除表中多餘的重複記錄，重複記錄是根據單個字段（peopleId）來判斷，只留有rowid最小的記錄 delete from people where peopleId  in (select  peopleId  from people  group  by  peopleId   having  count(peopleId) > 1) and rowid not in (select min(rowid) from  people  group by peopleId  having count(peopleId )>1) 三、查找表中多餘的重複記錄（多個字段） select * from vitae a where (a.peopleId,a.seq) in  (select peopleId,seq from vitae group by peopleId,seq  having count(*) > 1) 四、刪除表中多餘的重複記錄（多個字段），只留有rowid最小的記錄 delete from vitae a where (a.peopleId,a.seq) in  (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1) and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1) 五、查找表中多餘的重複記錄（多個字段），不包含rowid最小的記錄 select * from vitae a where (a.peopleId,a.seq) in  (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1) and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)