可在SQL Server和MS Access中使用的COALESCE，IFNULL或NZ()函数 [英] COALESCE, IFNULL, or NZ() function that can be used in SQL Server and MS Access

问题描述

我有一个可以使用SQL Server或MS Access作为数据存储的项目.在一个SELECT语句中，我必须对单个列和单个值执行COALESCE操作，如下所示:

I have a project that can use either SQL Server or MS Access as the data store. In one SELECT statement, I must perform a COALESCE operation on a single column and a single value, like this:

SELECT COALESCE([Amount], 0) FROM PaymentsDue;

我想编写一条将在SQL Server和MS Access中正确执行的SQL语句.最受关注的SQL Server版本是2008，尽管首选适用于各个版本的解决方案.

I would like to write a single SQL statement that will execute correctly in both SQL Server and MS Access. The SQL Server version that is of immediate interest is 2008, although a solution applicable across versions would be preferred.

今天早些时候，有人能够

Earlier today, someone was able to show me an SQL trick that allowed me to use a single SELECT statement to effectively CAST a DATETIME to DATE. I was wondering if anyone has a similar trick to perform a COALESCE (eg, IFNULL or NZ) operation in a way that can be applied to both SQL Server and MS Access?

推荐答案

这可以工作，但是很笨拙:

This will work, but it's clunky:

SELECT Amount 
FROM PaymentsDue
WHERE Amount IS NOT NULL
UNION ALL
SELECT 0 AS Amount 
FROM PaymentsDue
WHERE Amount IS NULL

很显然，如果您有多于一列，那么很快就会变得难以管理.

Obviously if you have more than one column, this gets to be quickly unmanageable.

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