在SQL Select语句中使用If else

I have a select statement which will return 2 columns.

我有一个select语句，它将返回两列。

ID | IDParent

Then in my program I have to test if IDParent is < 1 then use ID ELSE use IDParent

然后在我的程序中，我必须测试IDParent是否< 1，然后使用ID ELSE使用IDParent。

Is there a way to use an If Else like condition in SQL to return only single value?

是否有一种方法可以使用SQL中的If条件只返回单个值?

8 个解决方案

#1

you can use CASE

你可以用例

SELECT   ...,
         CASE WHEN IDParent < 1 THEN ID ELSE IDPArent END AS ColumnName,
         ...
FROM     tableName

#2

SELECT CASE WHEN IDParent < 1 
            THEN ID 
            ELSE IDParent 
       END AS colname 
FROM yourtable

#3

Here, using CASE Statement and find result:

在这里，用CASE语句找到结果:

select (case when condition1 then result1
             when condition2 then result2
             else result3
             end) as columnname from tablenmae:

For example:

例如:

select (CASE WHEN IDParent< 1 then ID 
             else IDParent END) as columnname
from tablenmae

#4

The query will be like follows

查询将如下所示。

SELECT (CASE WHEN tuLieuSo is null or tuLieuSo=''
            THEN 'Chưa có đĩa' 
            ELSE 'Có đĩa' End) AS tuLieuSo,moTa
FROM [gPlan_datav3_SQHKTHN].[dbo].[gPlan_HoSo]

#5

sql server 2012

  with
  student as 
(select sid,year from (
values (101,5),(102,5),(103,4),(104,3),(105,2),(106,1),(107,4)
) as student(sid,year)
)
select iif(year=5,sid,year) as myCol,* from student


 myCol  sid year
101 101 5
102 102 5
4   103 4
3   104 3
2   105 2
1   106 1
4   107 4

#6

You can also use a union construct. I'm not sure if CASE is a common SQL construct ...

您还可以使用联合构造。我不确定CASE是否是一个常见的SQL构造……

SELECT ID FROM tabName WHERE IDParent<1 OR IDParent IS NULL
UNION 
SELECT IDParent FROM tabName WHERE IDParent>1

#7

select 
CASE WHEN IDParent is < 1 then ID else IDParent END as colname 
from yourtable

#8

I Have a Query With This result :

我有一个关于这个结果的查询:

SELECT Top 3
 id,
 Paytype
 FROM dbo.OrderExpresses
 WHERE CreateDate > '2018-04-08'

The Result is :

其结果是:

22082   1
22083   2
22084   1

I Want Change The Code To String In Query, So I Use This Code :

我想在查询中将代码改为String，所以我使用了以下代码:

SELECT TOP 3
 id,
 CASE WHEN Paytype = 1 THEN N'Credit' ELSE N'Cash' END AS PayTypeString
 FROM dbo.OrderExpresses
 WHERE CreateDate > '2018-04-08'

And Result Is :)

结果是:)

22082   Credit
22083   Cash
22084   Credit

#1