Question

我有两张表SurrogateKeys和SurrogateKeyRelatives。

我会发现有些记录可以满足连接两个表的查询。

我正在玩两种选择：

select count(*) from 
(
    select top(1) sk.Username from SurrogateKeys as sk

    inner join SurrogateKeyRelatives as skr
    on sk.Id = skr.SurrKeyId

    where 

    sk.Username='John.Doe' and
    skr.SomeField = 1
)

和

if exists(
    select top(1) sk.Username from SurrogateKeys as sk

    inner join SurrogateKeyRelatives as skr
    on sk.Id = skr.SurrKeyId

    where 

    sk.Username='John.Doe' and
    skr.SomeField = 1
   )
   begin
    select 1
   end
else
    begin
      select 0
    end

尝试选项1会在＆＃39;）附近给出错误的语法。我在上面的查询中缺少什么？

Answer 1

select count(*) from 
(
    select top(1) sk.Username from SurrogateKeys as sk

    inner join SurrogateKeyRelatives as skr
    on sk.Id = skr.SurrKeyId

    where 

    sk.Username='John.Doe' and
    skr.SomeField = 1
) Q1

Answer 2

select top(1)  
       CASE 
          WHEN skr.SurrKeyId is null THEN 0 
          ELSE 1 
       END 
  from SurrogateKeys as sk
  left join SurrogateKeyRelatives as skr
    on sk.Id = skr.SurrKeyId
   and sk.Username='John.Doe' 
   and skr.SomeField = 1

Answer 3

第一个选项中的

尝试在大括号

之后给内部查询一个表名

select count(*) from 
(
    select top(1) sk.Username from SurrogateKeys as sk

    inner join SurrogateKeyRelatives as skr
    on sk.Id = skr.SurrKeyId

    where 

    sk.Username='John.Doe' and
    skr.SomeField = 1
) table1

从子选择语法中选择计数

3 个答案: