Question

我的存储过程中有以下代码：

CREATE MyProc
AS


CREATE TABLE #Table1 
(    
 Field1 INT NOT NULL,
 Field2 VARCHAR NULL,
 Field3 VARCHAR NULL,
 Field4 VARCHAR NULL

 );

-----填充临时表-----

INSERT INTO #Table1  (Field1)          
SELECT val1 FROM Tab1

INSERT INTO #Table1  (Field1,Field2)          
SELECT val1,"val2"  FROM Tab2

INSERT INTO #Table1  (Field1,Field2,Field3)          
SELECT val1,"val2","val3"  FROM Tab3

INSERT INTO #Table1  (Field1,Field2,Field3,Field4)          
SELECT val1,"val2","val3","val4"  FROM Tab3

SELECT Field1,Field2,Field3,Field4 FROM #Table1 
DROP #Table1

大约有10-15个INSERT语句正在填充临时表。我想调整存储过程以使用CTE或其他方式提高性能。我如何重写该过程？

Answer 1

我不完全确定这会以任何方式变得更好但是这是使用cte来获得相同的输出（我使用了一些lazy-ass值数组来使它开箱即用，你可以用实际的表来代替那些）：

with cte (f1, f2, f3, f4)
as (
    select 1, null, null, null
    from (
        values (1)
        ) t1(n1)

    union all

    select 1, 2, null, null
    from (
        values (1, 2)
        ) t1(n1, n2)

    union all

    select 1, 2, 3, null
    from (
        values (1, 2, 3)
        ) t1(n1, n2, n3)

    union all

    select 1, 2, 3, 4
    from (
        values (1, 2, 3, 4)
        ) t1(n1, n2, n3, n4)
    )
select *
from cte

将临时表代码转换为CTE以提高性能

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