SQL 完全连接表的条件

Question

我有同一个数据集的两个版本，我需要做一个完整的连接来找到其中一个丢失的记录，两个版本都有一些丢失的记录。我设法想出了两种方法，但都有缺点。我的数据集大小和过滤条件都非常大。

解决方案 1 有一个使用 CTE 的缺点，它会拆分过滤器并使代码更难阅读，我希望只有一个查询:

create table #temp (id int, vers nvarchar(1))
insert into #temp select 1,'a' union select 2,'a' union select 3,'a'
              union select 1,'b' union select 2,'b' union select 100,'b'

;WITH vers_a as (SELECT * FROM #temp WHERE vers = 'a')
,vers_b as (SELECT * FROM #temp WHERE vers = 'b')

SELECT ta.id, tb.id, ta.vers, tb.vers
FROM vers_a ta
FULL JOIN vers_b tb on ta.id = tb.id
WHERE ta.id is null or tb.id is null

drop table #temp

解决方案 2 复制过滤器，执行计划更大:

create table #temp (id int, vers nvarchar(1))
insert into #temp select 1,'a' union select 2,'a' union select 3,'a'
              union select 1,'b' union select 2,'b' union select 100,'b'

SELECT ta.id, tb.id, ta.vers, tb.vers
FROM #temp ta
FULL JOIN #temp tb on ta.id = tb.id and ta.vers = 'a' and tb.vers = 'b'
WHERE (ta.id is null or tb.id is null) and (ta.vers = 'a' or tb.vers = 'b')

drop table #temp

所以我的问题是，是否可以有类似解决方案 2 的东西，但没有双重条件定义和较小的执行计划，如解决方案 1？

编辑:在一个查询中运行两个解决方案时，我可以看到解决方案 2 成本为 26%，解决方案 1 成本为 45%，尽管它的执行计划较小。如果可能的话，我想要没有代码重复的更快的解决方案(不一定像我在问题中所说的那样具有更小的执行计划)。

Edit2:抱歉误导了第一次编辑，我不擅长优化 :) 我在大约 150 万行集上测试了这个，解决方案 1 更快，让集使用这个:

create table #temp (id int, vers nvarchar(1))
insert into #temp select 1,'a' union select 2,'a' union select 3,'a'
              union select 1,'b' union select 2,'b' union select 100,'b'
while (select count(*) from #temp) < 1000000
begin
    insert into #temp select id+ABS(CHECKSUM(NewId()))%10000, vers from #temp
end

Answer 1

这应该有一个很好的计划。 vers 上的索引可能会有所帮助。

SELECT ta.id, tb.id, ta.vers, tb.vers
FROM (SELECT * FROM #temp WHERE vers = 'a') ta
FULL JOIN (SELECT * FROM #temp WHERE vers = 'b') tb on ta.id = tb.id 
WHERE (ta.id is null or tb.id is null) 

编辑做了一些测试。上面的查询比其他 2 个版本有更好的 CPU。

-- SETUP
drop table temp;
go

create table temp (
   id int 
  ,vers nvarchar(1));

insert temp(id,vers)
select top(100000)
    row_number() over(order by (select null)) / 2  
  , case ABS(CHECKSUM(NewId())) % 2 when 0 then 'a' else 'b' end
from sys.all_objects t, sys.all_objects t1 ;


create index idx_temp_vers on temp(vers) include(id)
 with
  fillfactor=90;

select top(50) *
from temp;

-- TEST RUNS 
SET STATISTICS TIME ON;

print ' 1 index query 1 '
SELECT ta.id, tb.id, ta.vers, tb.vers
FROM (SELECT * FROM temp WHERE vers = 'a') ta
FULL JOIN (SELECT * FROM temp WHERE vers = 'b') tb on ta.id = tb.id 
WHERE (ta.id is null or tb.id is null)
;
print ' 1 index query 2 '
SELECT ta.id, tb.id, ta.vers, tb.vers
FROM temp ta
FULL JOIN temp tb on ta.id = tb.id and ta.vers = 'a' and tb.vers = 'b'
WHERE (ta.id is null or tb.id is null) and (ta.vers = 'a' or tb.vers = 'b')
;
print ' 1 index query 3 '
SELECT ta.id, TA.vers 
  from temp ta 
  where ta.vers = 'a' 
         and TA.id NOT IN(SELECT tb.id FROM temp tb WHERE tb.vers = 'b')
UNION ALL 
SELECT tb.id, Tb.vers 
  from temp tb 
  where tb.vers = 'b' 
         and Tb.id NOT IN(SELECT ta.id FROM temp ta WHERE ta.vers = 'a')

-- One more index
create index idx_temp_id on temp(id)
 with
  fillfactor=90;


print ' 2 indexes query 1 '
SELECT ta.id, tb.id, ta.vers, tb.vers
FROM (SELECT * FROM temp WHERE vers = 'a') ta
FULL JOIN (SELECT * FROM temp WHERE vers = 'b') tb on ta.id = tb.id 
WHERE (ta.id is null or tb.id is null)
;
print ' 2 indexes query 2 '
SELECT ta.id, tb.id, ta.vers, tb.vers
FROM temp ta
FULL JOIN temp tb on ta.id = tb.id and ta.vers = 'a' and tb.vers = 'b'
WHERE (ta.id is null or tb.id is null) and (ta.vers = 'a' or tb.vers = 'b')
;
print ' 2 indexes query 3 '
SELECT ta.id, TA.vers 
  from temp ta 
  where ta.vers = 'a' 
         and TA.id NOT IN(SELECT tb.id FROM temp tb WHERE tb.vers = 'b')
UNION ALL 
SELECT tb.id, Tb.vers 
  from temp tb 
  where tb.vers = 'b' 
         and Tb.id NOT IN(SELECT ta.id FROM temp ta WHERE ta.vers = 'a')


SET STATISTICS TIME OFF;

结果

 1 index query 1 
(49898 row(s) affected)
 SQL Server Execution Times:
   CPU time = 156 ms,  elapsed time = 3825 ms.

 1 index query 2 
(49898 row(s) affected)
 SQL Server Execution Times:
   CPU time = 281 ms,  elapsed time = 2962 ms.

 1 index query 3 
(49898 row(s) affected)
 SQL Server Execution Times:
   CPU time = 422 ms,  elapsed time = 2508 ms.

 2 indexes query 1 
(49898 row(s) affected)
 SQL Server Execution Times:
   CPU time = 172 ms,  elapsed time = 2679 ms.

 2 indexes query 2 
(49898 row(s) affected)
 SQL Server Execution Times:
   CPU time = 406 ms,  elapsed time = 3468 ms.

 2 indexes query 3 
(49898 row(s) affected)
 SQL Server Execution Times:
   CPU time = 407 ms,  elapsed time = 3728 ms.