如何在 NOT IN 子句中使用来自 select 语句的字符串列表

Question

我想建立一个姓氏列表，以便从第二个 select 语句的结果中过滤掉类似这样的东西（没有这样做）

DECLARE @ExcludedList VARCHAR(MAX)
SET @ExcludedList = (SELECT  TOP 20 Lastname
FROM dbo.Subscribers
where [Firstname] = 'Dave')

SELECT [Firstname], Count([Firstname]) as [Count] from Subscribers
WHERE [Lastname] not in (@ExcludedList)

Answer 1

为什么不能像

那样直接做

SELECT [Firstname], Count([Firstname]) as [Count] from Subscribers
WHERE [Lastname] not in (SELECT  TOP 20 Lastname
FROM dbo.Subscribers where [Firstname] = 'Dave')

嗯，我不确定你到底想达到什么目的，但考虑使用 table variable 并像下面那样使用

DECLARE @ExcludedList table(lastname varchar(30));
insert into @ExcludedList
SELECT  TOP 20 Lastname
FROM dbo.Subscribers where [Firstname] = 'Dave';

SELECT [Firstname], Count([Firstname]) as [Count] from Subscribers
WHERE [Lastname] not in (select lastname from @ExcludedList);

Answer 2

如果需要使用变量，则必须是table变量：

DECLARE @ExcludedList TABLE (Lastname VARCHAR(MAX))

INSERT INTO @ExcludedList
SELECT  TOP 20 Lastname
FROM dbo.Subscribers
WHERE [Firstname] = 'Dave'

SELECT [Firstname], Count([Firstname]) AS [Count] 
FROM Subscribers
WHERE [Lastname] NOT IN (SELECT Lastname FROM @ExcludedList)

如何在 NOT IN 子句中使用来自 select 语句的字符串列表

How can I use a string list from a select statement in a NOT IN clause

sql-server

select

dynamic

declare