如何在SQL SELECT语句中执行IF…THEN?
例如:
SELECT IF(Obsolete = 'N' OR InStock = 'Y' ? 1 : 0) AS Saleable, * FROM Product
如何在SQL SELECT语句中执行IF…THEN?
例如:
SELECT IF(Obsolete = 'N' OR InStock = 'Y' ? 1 : 0) AS Saleable, * FROM Product
当前回答
会是这样的:
SELECT OrderID, Quantity,
CASE
WHEN Quantity > 30 THEN "The quantity is greater than 30"
WHEN Quantity = 30 THEN "The quantity is 30"
ELSE "The quantity is under 30"
END AS QuantityText
FROM OrderDetails;
其他回答
Microsoft SQL Server(T-SQL)
在选择中,使用:
select case when Obsolete = 'N' or InStock = 'Y' then 'YES' else 'NO' end
在where子句中,使用:
where 1 = case when Obsolete = 'N' or InStock = 'Y' then 1 else 0 end
SELECT
(CASE
WHEN (Obsolete = 'N' OR InStock = 'Y') THEN 'YES'
ELSE 'NO'
END) as Salable
, *
FROM Product
SELECT 1 AS Saleable, *
FROM @Product
WHERE ( Obsolete = 'N' OR InStock = 'Y' )
UNION
SELECT 0 AS Saleable, *
FROM @Product
WHERE NOT ( Obsolete = 'N' OR InStock = 'Y' )
我喜欢使用CASE语句,但问题是在SQLSelect中使用IF语句。我过去使用的是:
SELECT
if(GENDER = "M","Male","Female") as Gender
FROM ...
这就像Excel或sheets IF语句,其中有一个条件,后跟true条件,然后是false条件:
if(condition, true, false)
此外,您还可以嵌套if语句(但use应该使用CASE:-)
(注意:这在MySQL Workbench中有效,但在其他平台上可能不起作用)
问题:
SELECT IF(Obsolete = 'N' OR InStock = 'Y' ? 1 : 0) AS Saleable, * FROM Product
答案:
Select
case when p.Obsolete = 'N'
or p.InStock = 'Y' then 1 else 0 end as Saleable,
p.*
FROM
Product p;
使用别名(在本例中为p)将有助于防止出现问题。