在TSQL过程中使用输出参数，然后在游标中调用该过程以更新表？

问题描述

我尝试过更改程序中的表；但是，鉴于该表是在之后创建或删除的，所以这行不通吗？

在此之前，我尝试创建表，然后将过程中的值插入表中。失败了甚至没有运行。

无论我做什么，（表值）tvWin始终为空...

目标是创建一个石头剪刀布游戏，并使用游标遍历值表“ Rock / paper / scissors”。我想那部分很容易。

我只得到tvWin的空值。我猜这意味着在转移过程以更新表值时遇到问题。

这似乎非常令人费解，但这就是我应该做的。在过程中创建变量，创建要运行的代码；在过程外部创建空变量以存储游标的迭代值；然后，从游标中的过程中调用值。我的意思是，这开始像Inception。

工作光标代码：

使用scratch_DB;

DROP TABLE IF EXISTS tblRPS_data;

GO
-----

CREATE TABLE tblRPS_data
(
 tvSeq INT IDENTITY PRIMARY KEY,tvP1 CHAR(1),tvP2 CHAR(1),tvWin CHAR(1)
);

GO
-----

INSERT INTO tblRPS_data(tvP1,tvP2)
VALUES ( 'R','R' ),( 'R','P' ),'S' ),( 'P',( 'S','S' );

DECLARE @lvSeq CHAR(1),@lvP1 CHAR(1),@lvP2 CHAR(1),@lvWin CHAR(1);

IF CURSOR_STATUS('global','csrMyCursor')>=-1
BEGIN
 DEALLOCATE csrMyCursor;
END

 DECLARE csrMyCursor CURSOR
    FOR
    SELECT tvSeq,tvP1,tvP2
    FROM tblRPS_data;

OPEN csrMyCursor;

FETCH NEXT FROM csrMyCursor
INTO @lvSeq,@lvP1,@lvP2;

WHILE (@@FETCH_STATUS = 0)

BEGIN

IF @lvP1 NOT IN ('R','P','S') OR @lvP1 NOT IN ('R','S')
    SET @lvWin = 0;

    ELSE IF @lvP1 + @lvP2 IN ('RS','PR','SP')
        SET @lvWin = 1;

        ELSE IF @lvP1 = @lvP2 
        SET @lvWin=3;

        ELSE 
        SET @lvWin = 2;

        IF @lvWin = 3
        PRINT 'It is a tie'
        
        ELSE 
        PRINT 'The Winner is Player ' + @lvWin;

UPDATE tblRPS_data
SET tvWin = @lvWin
WHERE tvSeq=@lvSeq;

FETCH NEXT FROM csrMyCursor
INTO @lvSeq,@lvP2;

END

CLOSE csrMyCursor;
DEALLOCATE csrMyCursor;

SELECT *
FROM tblRPS_data;

输出很好。

现在，如何将这个过程放在光标中而不是直接代码中？

USE scratch_DB;

GO

CREATE OR ALTER PROCEDURE udpCalcWinner( @parmP1 AS CHAR(1),@parmP2 AS CHAR(1) ) --creates procedure (program) with 2 inputs

AS 

BEGIN

DECLARE @lvP1 AS CHAR(1),@lvP2 AS CHAR(1),@lvWin AS TINYINT;

IF @lvP1 NOT IN ('R','SP')
        SET @lvWin = 1;

        ELSE IF @lvP1 = @lvP2 
        SET @lvWin=3;

        ELSE 
        SET @lvWin = 2;

    RETURN 0;

END;

DROP TABLE IF EXISTS tblRPS_data;

CREATE TABLE tblRPS_data
(
 tvSeq INT IDENTITY PRIMARY KEY,tvP2)
VALUES  ( 'R','S' );

DECLARE @lvSeq AS INT,@lvP1 AS CHAR(1),@lvWin AS CHAR(1);

IF CURSOR_STATUS('global',@lvP2;

WHILE (@@FETCH_STATUS = 0)
-------------------------------------------
BEGIN

DECLARE @lvI AS INT;
    
EXECUTE @lvI = udpCalcWinner '@lvP1','@lvP2';

    UPDATE tblRPS_data
    SET tvWin = @lvWin
    WHERE tvSeq = @lvSeq;

    FETCH NEXT FROM csrMyCursor
    INTO @lvSeq,@lvP2;
END;

CLOSE csrMyCursor;
DEALLOCATE csrMyCursor;

SELECT * 
FROM tblRPS_data;

结果应该是9行；并且，tvWin列中的所有Null值都与游标代码不同。

解决方法

create procedure udpCalcWinner @lvP1 char(1),@lvP2 char(1),@lvWin char(1) output
.......
select @lvP1 = isnull(@lvP1,'-'),@lvP2 = isnull(@lvP2,'-') --handle null input

IF @lvP1 NOT IN ('R','P','S') OR @lvP2 NOT IN ('R','S')
    SET @lvWin = '0'; --@lvWin is char...quotes ''
..............................................................
        else if @lvWin = '0'
        print 'invalid input'

        ELSE 
        PRINT 'The Winner is Player ' + @lvWin;
GO

 .........cursor loop .........
 EXECUTE udpCalcWinner @lvP1 = @lvP1,@lvP2=@lvP2,@lvWin = @lvWin output;