如何在 C# 中显示 SQL“PRINT”命令的输出？

Question

我有一个总是返回“PRINT”命令的 SQL 过程，我想提取这个“PRINT”命令的输出，即 C# 中的过程我该怎么做？这是程序

ALTER PROC ResultsPoll
@pollid INT 
AS
DECLARE @count1 INT 
DECLARE @count2 INT 
DECLARE @count3 INT 
DECLARE @count4 INT 
DECLARE @count5 INT 
DECLARE @test VARCHAR(MAX)
DECLARE @value VARCHAR(MAX)
SELECT @count1 = COUNT(mem_id) FROM Students_answer_Polls INNER JOIN Polls ON Polls.poll_id = Students_answer_Polls.poll_id
WHERE Students_answer_Polls.poll_id = @pollid AND Students_answer_Polls.answer = Polls.a1
SELECT @count2 = COUNT(mem_id) FROM Students_answer_Polls INNER JOIN Polls ON Polls.poll_id = Students_answer_Polls.poll_id
WHERE Students_answer_Polls.poll_id = @pollid AND Students_answer_Polls.answer = Polls.a2
SELECT @count3 = COUNT(mem_id) FROM Students_answer_Polls INNER JOIN Polls ON Polls.poll_id = Students_answer_Polls.poll_id
WHERE Students_answer_Polls.poll_id = @pollid AND Students_answer_Polls.answer = Polls.a3
SELECT @count4 = COUNT(mem_id) FROM Students_answer_Polls INNER JOIN Polls ON Polls.poll_id = Students_answer_Polls.poll_id
WHERE Students_answer_Polls.poll_id = @pollid AND Students_answer_Polls.answer = Polls.a4
SELECT @count5 = COUNT(mem_id) FROM Students_answer_Polls INNER JOIN Polls ON Polls.poll_id = Students_answer_Polls.poll_id
WHERE Students_answer_Polls.poll_id = @pollid AND Students_answer_Polls.answer = Polls.a5

SELECT @test=Polls.a1 FROM Polls WHERE poll_id = @pollid
IF(@test IS NOT NULL)
BEGIN
PRINT ('Number of students who chose '+@test+' is:'+' '+CAST (@count1 AS VARCHAR(MAX)))
END
SELECT @test=Polls.a2 FROM Polls WHERE poll_id = @pollid
IF(@test IS NOT NULL)
BEGIN
PRINT ('Number of students who chose '+@test+' is:'+' '+CAST (@count2 AS VARCHAR(MAX)))
END
SELECT @test=Polls.a3 FROM Polls WHERE poll_id = @pollid
IF(@test IS NOT NULL)
BEGIN
PRINT ('Number of students who chose '+@test+' is:'+' '+CAST (@count3 AS VARCHAR(MAX)))
END
SELECT @test=Polls.a4 FROM Polls WHERE poll_id = @pollid
IF(@test IS NOT NULL)
BEGIN
PRINT ('Number of students who chose '+@test+' is:'+' '+CAST (@count4 AS VARCHAR(MAX)))
END
SELECT @test=Polls.a5 FROM Polls WHERE poll_id = @pollid
IF(@test IS NOT NULL)
BEGIN
PRINT ('Number of students who chose '+@test+' is:'+' '+CAST (@count5 AS VARCHAR(MAX)))
END

Answer 1

您需要订阅SqlConnection.InfoMessage 事件。

MSDN 有一些示例代码here。

Answer 2

正确的做法是将值记录在输出参数中，然后在存储过程中打印输出参数值。

例如：

ALTER PROC ResultsPoll
@pollid INT ,
@message varchar(max) OUTPUT
AS
SET @message = ''
...
IF(@test IS NOT NULL)
BEGIN
SET @message = 'Number of students who chose '+@test+' is:'+' '+CAST (@count1 AS VARCHAR(MAX))
END
...

PRINT(@message)

然后，在您的代码中，检索输出参数的值。

更新

仅当返回单个状态或错误消息时，上述建议才有效。仔细查看存储过程后，我意识到此存储过程并非如此，因为打印语句用于将数据返回给调用应用程序。

既然我明白了这一点，我建议，如果可能的话，将存储过程重写如下：

ALTER PROC ResultsPoll
@pollid INT 
AS

SELECT result = 'Number of students who chose ' + MAX(Polls.a1) + ' is: ' + CAST(COUNT(1) AS NVARCHAR(MAX)) 
  FROM Students_answer_Polls INNER JOIN Polls ON Polls.poll_id = Students_answer_Polls.poll_id
 WHERE Students_answer_Polls.poll_id = @pollid AND Students_answer_Polls.answer = Polls.a1

UNION

SELECT result = 'Number of students who chose ' + MAX(Polls.a2) + ' is: ' + CAST(COUNT(1) AS NVARCHAR(MAX)) 
  FROM Students_answer_Polls INNER JOIN Polls ON Polls.poll_id = Students_answer_Polls.poll_id
 WHERE Students_answer_Polls.poll_id = @pollid AND Students_answer_Polls.answer = Polls.a2

UNION

SELECT result = 'Number of students who chose ' + MAX(Polls.a3) + ' is: ' + CAST(COUNT(1) AS NVARCHAR(MAX)) 
  FROM Students_answer_Polls INNER JOIN Polls ON Polls.poll_id = Students_answer_Polls.poll_id
 WHERE Students_answer_Polls.poll_id = @pollid AND Students_answer_Polls.answer = Polls.a3

UNION

SELECT result = 'Number of students who chose ' + MAX(Polls.a4) + ' is: ' + CAST(COUNT(1) AS NVARCHAR(MAX)) 
  FROM Students_answer_Polls INNER JOIN Polls ON Polls.poll_id = Students_answer_Polls.poll_id
 WHERE Students_answer_Polls.poll_id = @pollid AND Students_answer_Polls.answer = Polls.a4

UNION

SELECT result = 'Number of students who chose ' + MAX(Polls.a5) + ' is: ' + CAST(COUNT(1) AS NVARCHAR(MAX)) 
  FROM Students_answer_Polls INNER JOIN Polls ON Polls.poll_id = Students_answer_Polls.poll_id
 WHERE Students_answer_Polls.poll_id = @pollid AND Students_answer_Polls.answer = Polls.a5

有了这个，您可以只处理返回的行，这将有一个名为 result 的列。