带有 ISNULL 的选择语句

发布于 2024-09-25 15:51:24 字数 297 浏览 6 评论 0原文

我正在编写一个存储过程，在该过程中我使用 isNULL。如果值为空，我想使用 select 语句作为替换值，这可能吗？

IF ISNULL(@v_FilePrefix, (SELECT @v_FilePrefix = TransactionTypePrefix 
                            FROM [ConfigTransactionType] 
                           WHERE TransactionTypeID = @TransactionTypeID));

原文

I am writing a stored procedure and within this procedure I am using isNULL. If the value is null I want to use a select statement as the replacement value is this even possible?

IF ISNULL(@v_FilePrefix, (SELECT @v_FilePrefix = TransactionTypePrefix 
                            FROM [ConfigTransactionType] 
                           WHERE TransactionTypeID = @TransactionTypeID));

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雪落纷纷 2024-10-02 15:51:24

你可以用这个：

IF @v_FilePrefix IS NULL
BEGIN

    SELECT @v_FilePrefix = TransactionTypePrefix
    FROM [ConfigTransactionType]
    WHERE TransactionTypeID = @TransactionTypeID

END

我想这就是你想要的？

You can use this:

IF @v_FilePrefix IS NULL
BEGIN

    SELECT @v_FilePrefix = TransactionTypePrefix
    FROM [ConfigTransactionType]
    WHERE TransactionTypeID = @TransactionTypeID

END

I think this is what you're after?

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半山落雨半山空 2024-10-02 15:51:24

假设 @TransactionTypeID 将始终返回一个值：

SELECT @v_FilePrefix = COALESCE(@v_FilePrefix, TransactionTypePrefix)
  FROM [ConfigTransactionType] 
 WHERE TransactionTypeID = @TransactionTypeID

COALESCE 将返回第一个非空值。如果@v_FilePrefix不为空，它只会将该值设置为其自身。

但最好使用：

IF @v_FilePrefix IS NULL
BEGIN

   SELECT @v_FilePrefix = TransactionTypePrefix
     FROM [ConfigTransactionType]
    WHERE TransactionTypeID = @TransactionTypeID

END

Assuming the @TransactionTypeID will always return a value:

SELECT @v_FilePrefix = COALESCE(@v_FilePrefix, TransactionTypePrefix)
  FROM [ConfigTransactionType] 
 WHERE TransactionTypeID = @TransactionTypeID

COALESCE will return the first non-null value. If @v_FilePrefix is not null, it will just set the value to itself.

But it would be best to use:

IF @v_FilePrefix IS NULL
BEGIN

   SELECT @v_FilePrefix = TransactionTypePrefix
     FROM [ConfigTransactionType]
    WHERE TransactionTypeID = @TransactionTypeID

END

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