Using If else in SQL Select statement

Question

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

Answer 1

you can use CASE

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

Answer 2

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

Answer 3

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 ;

Answer 4

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

Answer 5

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]

Answer 6

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