sql语句的多种写法

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精妙SQL语句

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精妙SQL语句介绍

Oracle Union All Query

根据指定ID，返回包含该ID的所有父级记录

一个DETAIL 表，
item ,empid, money
1       001    100
2       001     150
...    ...     ...

一个 TOTAL 表，
empid ,  money
目的是想把DETAIL 表的每个empid 的数据汇总插入到TOTAL 表中，
写的语句是这样地，
写法1：
  update total a set
 money=(select sum(nvl(money,0))
  from detail  where a.empid= empid group by
empid  )

写法2：（有些不通用）
drop table total;
create table total as select empid,sum(nvl(money,0)) money from detail group by empid;
写法3：
update total a set
 money=(select sum(nvl(money,0))
  from detail where a.empid= empid )
写法4：
update total a set
               money=(select sum(nvl(b.money,0))
               from detail b where a.empid=b.empid )
where exists (select 1 from detail b where a.empid=b.empid );

Q]如何使用Hint提示
[A] 在select/delete/update后写/*+ hint */
如 select /*+ index(TABLE_NAME INDEX_NAME) */ col1...
注意/*和+之间不能有空格
如用hint指定使用某个索引

  select /*+ index(cbotab) */ col1 from cbotab;
  select /*+ index(cbotab cbotab1) */ col1 from cbotab;
  select /*+ index(a cbotab1) */ col1 from cbotab a;
  其中
   TABLE_NAME是必须要写的，且如果在查询中使用了表的别名，在hint也要用表的别名来代替表名;
INDEX_NAME可以不必写，Oracle会根据统计值选一个索引;
   如果索引名或表名写错了，那这个hint就会被忽略;

 

CREATE PROCEDURE dbo.PostGetPostByPage  (   @page int,   @forumid int,   @topornot int  ) AS  /* SET NOCOUNT ON */  declare @begin int,@end int,@f int,@l int,@count int,@top int    select @top=count(*) from Posts as p1 where p1.PostID=(select min(PostID) from Posts as p2 where p1.ThreadID=p2.ThreadID)  and p1.ForumID=@forumid and PostType=4    if @topornot=1    select p1.PostType,p1.Title,p1.UserName,p1.TotalViews,p1.PostID,p1.ThreadID,p1.ForumID,FileName,  Reply=(select Count(*) from Posts as p2 where p1.ThreadID=p2.ThreadID)-1,  LastDate=(select Max(PostDate)from Posts as p2 where p1.ThreadID=p2.ThreadID),  LastWriter=(select UserName from posts as p2 where p2.PostID=(select Max(PostID)from Posts as p2 where p1.ThreadID=p2.ThreadID))  from Posts as p1 where p1.PostID=(select min(PostID) from Posts as p2 where p1.ThreadID=p2.ThreadID)  and p1.ForumID=@forumid and PostType=4    else if @topornot=2  begin    select @count=count(*) from Posts as p1 where p1.PostID=(select min(PostID) from Posts as p2 where p1.ThreadID=p2.ThreadID)  and p1.ForumID=@forumid and PostType<>4    declare my_cursor SCROLL CURSOR for  select p1.PostID from Posts as p1 where p1.PostID=(select min(PostID) from Posts as p2 where p1.ThreadID=p2.ThreadID)  and p1.ForumID=@forumid and PostType<>4 order by (select max(PostID) from Posts as p2 where p1.ThreadID=p2.ThreadID) desc  open my_cursor        if @count+@top<25 and @page=1  begin  select @f=1  select @l=@count  end  if @count+@top>=25 and @page=1  begin  select @f=1  select @l=25-@top  end    if(@page*25-@top>@count) and @page>1  begin  select @f=(@page-1)*25+1-@top  select @l=@count  end  if(@page*25-@top<=@count) and @page>1  begin  select @f=(@page-1)*25+1-@top  select @l=@page*25-@top  end      fetch absolute @f from my_cursor into @begin  fetch absolute @l from my_cursor into @end  set nocount off     select p1.PostType,p1.Title,p1.UserName,p1.TotalViews,p1.PostID,p1.ThreadID,p1.ForumID,FileName,  Reply=(select Count(*) from Posts as p2 where p1.ThreadID=p2.ThreadID)-1,  LastDate=(select Max(PostDate)from Posts as p2 where p1.ThreadID=p2.ThreadID),  LastWriter=(select UserName from posts as p2 where p2.PostID=(select Max(PostID)from Posts as p2 where p1.ThreadID=p2.ThreadID))  from Posts as p1 where p1.PostID=(select min(PostID) from Posts as p2 where p1.ThreadID=p2.ThreadID)  and p1.ForumID=@forumid and PostID<=@begin and PostID>=@end and PostType<>4 order by (select max(PostID) from Posts as p2 where p1.ThreadID=p2.ThreadID) desc    close my_cursor  end  RETURN @@Rowcount GO ---------- 以下为一数据内容: 字段: 员工卡号(nvarchar) 打卡日期(smalldatetime) 打卡时间(smalldatetime)           687623            2004-5-26              2004-5-26 7:29:00           687623            2004-5-26              2004-5-26 11:5:00           687623            2004-5-26              2004-5-26 13:31:00           687623            2004-5-26              2004-5-26 17:33:00           687244            2004-5-26              2004-5-26 7:35:00           687244            2004-5-26              2004-5-26 11:1:00           687244            2004-5-26              2004-5-26 13:28:00           687244            2004-5-26              2004-5-26 17:24:00             :                   :                         :             :                   :                         :             :                   :                         : 需达到以下效果:          员工卡号            打卡日期            打卡明细时间           687623            2004-5-26     7:29 11:5 13:31 17:33           687244            2004-5-26     7:35 11:1 13:28 17:24 其中, 打卡明细时间由上表的打卡时间而来 --创建一个合并处理函数(生成打卡明细时间) create function f_time( @员工卡号 nvarchar(6), @打卡日期 smalldatetime )returns varchar(8000) as begin  declare @re varchar(8000)  set @re=''  select @re=@re+' '+convert(char(5),打卡时间,108)  from 数据表  where 员工卡号=@员工卡号 and 打卡日期=@打卡日期  return(stuff(@re,1,1,'')) end go --调用函数实现查询 select 员工卡号,打卡日期,打卡明细时间=dbo.f_time(员工卡号,打卡日期) from 数据表 group by 员工卡号,打卡日期