sql-server - 游标循环内的表变量

Question

我注意到，当我在游标循环中声明一个表变量时，该变量会在游标生命周期内持续存在。我的问题是，是否有一种方法可以声明变量，使其生命周期只会在迭代中持续存在？这是一个示例:

DECLARE @SourceTable TABLE(Id INT IDENTITY(1,1),Remarks VARCHAR(10))
INSERT INTO @SourceTable VALUES ('First')
INSERT INTO @SourceTable VALUES ('Second')
INSERT INTO @SourceTable VALUES ('Third ')

/* declare variables */
DECLARE @variable INT

DECLARE my_cursor CURSOR FAST_FORWARD READ_ONLY FOR SELECT Id FROM @SourceTable

OPEN my_cursor

FETCH NEXT FROM my_cursor INTO @variable

WHILE @@FETCH_STATUS = 0
BEGIN
    --Dose not creates a new instance
    DECLARE @VarTable TABLE (Remarks VARCHAR(10))

    INSERT INTO @VarTable
    SELECT TOP 1 Remarks FROM @SourceTable
    WHERE Id = @variable


    --Works as intended if you drop when done
    CREATE TABLE #TempTable  (Remarks VARCHAR(10))

    INSERT INTO #TempTable
    SELECT TOP 1 Remarks FROM @SourceTable
    WHERE Id = @variable

    DROP TABLE #TempTable

    FETCH NEXT FROM my_cursor INTO @variable
END

CLOSE my_cursor
DEALLOCATE my_cursor

SELECT * FROM @VarTable

但它变得更加困惑。如果你试图查询游标外的 temptable，你会得到一个错误。似乎临时表是这种情况的唯一正确方法？

Answer 1

TSQL 变量的范围是从它的声明到批处理结束。

所以在游标内部的每个循环中，您都需要从表变量中删除数据

我知道在声明游标内的每个循环表变量时很奇怪，但这就是它的工作方式

在外部声明表变量并在CURSOR内部执行Insert/Delete语句

DECLARE @VarTable TABLE (Remarks VARCHAR(10))

DECLARE my_cursor CURSOR FAST_FORWARD READ_ONLY FOR SELECT Id FROM @SourceTable

OPEN my_cursor
.......
.......
  DROP TABLE #TempTable

  DELETE FROM @VarTable

  FETCH NEXT FROM my_cursor INTO @variable
END
....