在 SQL 服务器中使用游标（可能带有连接）重写查询

Question

我有一个查询（不是我自己写的），我正在努力使其运行更快。我好像是这个

看不到答案是否适用于我的情况。是否可以重写此查询？

结构是：

TRUNCATE TABLE TableA

declare @myvar as varchar(255)


declare cur CURSOR LOCAL FAST_FORWARD
for SELECT SUB_TRANS
    FROM TableB
open cur

fetch next from cur 
into @myvar

while @@FETCH_STATUS = 0 
BEGIN

    INSERT INTO TableA
    SELECT many_thing
    from 4_tables_with_join(Note: @myvar is included as a join condition)



    fetch next from cur 
    into @myvar

END

close cur
deallocate cur

Answer 1

作为“一般提示”：您很可能根本不需要游标逻辑。我建议将其重写为直接 insert ... select 查询。

作为 pseudo-code，这看起来像：

insert into tablea (col1, col2, ...)
select many_thing
from tableb tb
inner join ... -- use "tb.subtrans" here in the join conditions instead of "@myvar"

在 SQL 服务器中使用游标（可能带有连接）重写查询

Rewrite query using cursor (perhaps with a join) in SQL Server

tsql

sql-server

stored-procedures

inner-join

sql-insert