Using If else in SQL Select statement

I have a select statement which will return 2 columns.

ID | IDParent 

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

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

11 Answers

you can use CASE

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

Here, using CASE Statement and find result:

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

For example:

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

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

The query will be like follows

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] 

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 

You can use simply if statement under select query as like I have described below

if(some_condition,if_satisfied,not_satisfied)

SELECT IF(IDParent < 1,ID,IDParent) FROM yourTable ; 

Here is some example using CASE WHEN

SELECT CASE WHEN A > 1 THEN 'Greater than 1' END FROM TRIANGLES 

.

SELECT CASE WHEN A > 1 THEN A END FROM TRIANGLES 

.

SELECT CASE WHEN A > 1 and B > 1 THEN 'Greater than 1' END FROM TRIANGLES 

.

SELECT CASE WHEN A > 1 THEN 'greater than 1' ELSE 'less than 1' END FROM TRIANGLES 

.

SELECT CASE WHEN A > 1 THEN 'greater than 1' ELSE CASE WHEN A >= 0 THEN 'greater than or equal 0' ELSE 'less than 0' END END FROM TRIANGLES; 

Hope this helps

Here are two ways "IF" Or "CASE".

SELECT IF(COLUMN_NAME = "VALUE", "VALUE_1", "VALUE_2") AS COLUMN_NAME FROM TABLE_NAME; 

OR

SELECT (CASE WHEN COLUMN_NAME = "VALUE" THEN 'VALUE_1' ELSE 'VALUE_2' END) AS COLUMN_NAME FROM TABLE_NAME; 

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

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

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

I Have a Query With This result :

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

The Result is :

22082 1 22083 2 22084 1 

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

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 :)

22082 Credit 22083 Cash 22084 Credit