sql-server - 如何在 SQL Server 中编写 foreach？

Question

我正在尝试实现类似于 for-each 的功能，我想获取返回的 select 语句的 Id 并使用它们中的每一个。

DECLARE @i int
DECLARE @PractitionerId int
DECLARE @numrows int
DECLARE @Practitioner TABLE (
    idx smallint Primary Key IDENTITY(1,1)
    , PractitionerId int
)

INSERT @Practitioner
SELECT distinct PractitionerId FROM Practitioner

SET @i = 1
SET @numrows = (SELECT COUNT(*) FROM Practitioner)
IF @numrows > 0
    WHILE (@i <= (SELECT MAX(idx) FROM Practitioner))
    BEGIN

        SET @PractitionerId = (SELECT PractitionerId FROM @Practitioner WHERE idx = @i)

        --Do something with Id here
        PRINT @PractitionerId

        SET @i = @i + 1
    END

目前我有一些类似于上面的内容，但收到错误:

Invalid column name 'idx'.

Answer 1

您似乎想要使用CURSOR。尽管大多数时候最好使用基于集合的解决方案，但有时 CURSOR 是最佳解决方案。在不了解您真正问题的情况下，我们无法为您提供更多帮助:

DECLARE @PractitionerId int

DECLARE MY_CURSOR CURSOR 
  LOCAL STATIC READ_ONLY FORWARD_ONLY
FOR 
SELECT DISTINCT PractitionerId 
FROM Practitioner

OPEN MY_CURSOR
FETCH NEXT FROM MY_CURSOR INTO @PractitionerId
WHILE @@FETCH_STATUS = 0
BEGIN 
    --Do something with Id here
    PRINT @PractitionerId
    FETCH NEXT FROM MY_CURSOR INTO @PractitionerId
END
CLOSE MY_CURSOR
DEALLOCATE MY_CURSOR