SQL查询，如果值为null，则返回1

我有一个查询，返回在我们的系统中设置的汇率值。 不是每个订单都有一个汇率（currate.currentrate），所以它返回空值。

我可以得到它返回1而不是null？

像if语句这样的东西可能是：

if isnull(currate.currentrate) then 1 else currate.currentrate 

这是我的查询下面。 我非常感谢你的帮助！

  SELECT orderhed.ordernum, orderhed.orderdate, currrate.currencycode, currrate.currentrate FROM orderhed LEFT OUTER JOIN currrate ON orderhed.company = currrate.company AND orderhed.orderdate = currrate.effectivedate 

Answer 1

您可以使用CASE语句。

 SELECT CASE WHEN currate.currentrate IS NULL THEN 1 ELSE currate.currentrate END FROM ... 

Answer 2

你可以使用COALESCE ：

 SELECT orderhed.ordernum, orderhed.orderdate, currrate.currencycode, coalesce(currrate.currentrate, 1) as currentrate FROM orderhed LEFT OUTER JOIN currrate ON orderhed.company = currrate.company AND orderhed.orderdate = currrate.effectivedate 

甚至IsNull() ：

 SELECT orderhed.ordernum, orderhed.orderdate, currrate.currencycode, IsNull(currrate.currentrate, 1) as currentrate FROM orderhed LEFT OUTER JOIN currrate ON orderhed.company = currrate.company AND orderhed.orderdate = currrate.effectivedate 

这里有一篇文章帮助决定COALESCE和IsNull ：

http://www.mssqltips.com/sqlservertip/2689/deciding-between-coalesce-and-isnull-in-sql-server/

Answer 3

 SELECT ISNULL(currate.currentrate, 1) FROM ... 

是比获胜的答案less冗长，并做同样的事情

https://msdn.microsoft.com/en-us/library/ms184325.aspx

Answer 4

 SELECT orderhed.ordernum, orderhed.orderdate, currrate.currencycode, case(currrate.currentrate) when null then 1 else currrate.currentrate end FROM orderhed LEFT OUTER JOIN currrate ON orderhed.company = currrate.company AND orderhed.orderdate = currrate.effectivedate 

Answer 5

尝试像下面…

 CASE WHEN currate.currentrate is null THEN 1 ELSE currate.currentrate END as currentrate 

Answer 6

a）如果当值为null时你想要0

 SELECT isnull(PartNum,0) AS PartNumber, PartID FROM Part 

b）如果你希望0值为空，否则为1

 SELECT (CASE WHEN PartNum IS NULL THEN 0 ELSE 1 END) AS PartNumber, PartID FROM Part