TSQL 控制流逻辑

Question

我正在构建一个使用基本动态 SQL 的程序。我想在所述过程的另一部分中使用动态 SQL (@query) 的结果。下面是我试图完成的代码的 shorthand 版本。

如果不使用 sp_executesql，我该如何将 @query 的结果值传递到 IF 块中？

DECLARE @table VARCHAR(MAX)
DECLARE @query VARCHAR(MAX)
DECLARE @map VARCHAR(MAX)

SET @table = 'SomeTable'

SET @query = '
;WITH Assignment AS 
(
SELECT 
''' + @table + ''' AS src
,Type
,RANK () OVER(ORDER BY COUNT(type) as rnk
FROM ' + @table + '
GROUP BY Type
)
SELECT Type
FROM Assignment
WHERE rnk = ''1'''

IF (@query = 'typeA')
BEGIN
/* preform an upsert dynamically */
END

IF (@query = 'typeB')
BEGIN
/* preform a delete dynamically */
END

IF (@query = 'typeC')
BEGIN
/* preform an alter dynamically */
END

Answer 1

为什么在设置了一些 SQL 后立即测试 @query？

你可以用临时的 table:

Create Table #temp(type...)
SET @query = '
;WITH Assignment AS 
(
SELECT 
''' + @table + ''' AS src
,Type
,RANK () OVER(ORDER BY COUNT(type) as rnk
FROM ' + @table + '
GROUP BY Type
)
Insert Into #temp(type)
SELECT Type
FROM Assignment
WHERE rnk = ''1'''

您还可以在 if 语句中构建动态查询，但我不确定它是否适用于您的情况：

SET @q1 = '
;WITH Assignment AS 
(
SELECT 
''' + @table + ''' AS src
,Type
,RANK () OVER(ORDER BY COUNT(type) as rnk
FROM ' + @table + '
GROUP BY Type
)'
set @q2 = 'SELECT Type
FROM Assignment
WHERE rnk = ''1'''

Case When @type = 'A' then @query = @q1 + 'Insert into... ' + @q2 
Case When @type = 'B' then @query = @q1 + 'Update... ' + @q2 
Case When @type = 'B' then @query = @q1 + 'delete from where type in (' + @q2 + ')' end

如果你改变主意，也很容易 sp_executesql:

create table #temp(type int)
insert into #temp 
exec sp_executesql @query

或者如果没有数千行：

declare @temp table(type int)
insert into @temp
exec sp_executesql @query

如果只有一行，还是sp_executesql和一个参数，这是最好的选择：

declare @type varchar(10)
SET @query = '
    declare @type varchar(10)    
;WITH Assignment AS 
(
SELECT 
''' + @table + ''' AS src
,Type
,RANK () OVER(ORDER BY COUNT(type) as rnk
FROM ' + @table + '
GROUP BY Type
)
SELECT @type = Type
FROM Assignment
WHERE rnk = ''1''';

exec sp_executesql @query, N'@type varchar(10)', @type = @type

Answer 2

这是从动态中获取数据的一种方法SQL

DECLARE @SQL VARCHAR(MAX)

--Dynamic SQL
SET @SQL = '
--Do anything you like in here as long as you select the results in the @Data Table format at the end
SELECT 132'

--How to get the result out of the dynamic SQL (into a table)
DECLARE @Data TABLE (Value INT)
INSERT INTO @Data(Value)
EXEC(@SQL)

--Get the result out of the table into a local (if you need to)
DECLARE @MyValue INT

SELECT @MyValue  = Value FROM @Data

--Do what you like with the value now we are back in normal SQL
PRINT @MyValue

TSQL 控制流逻辑

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