How do I perform an IF...THEN in an SQL SELECT?

Eric_Labashosky_6522 0
Viewed 4252690

How do I perform an IF...THEN in an SQL SELECT statement?

For example:

SELECT IF(Obsolete = 'N' OR InStock = 'Y' ? 1 : 0) AS Saleable, * FROM Product
if-statement case tsql sql-server sql
33 Answers

The CASE statement is the closest to IF in SQL and is supported on all versions of SQL Server.

SELECT CAST(
             CASE
                  WHEN Obsolete = 'N' or InStock = 'Y'
                     THEN 1
                  ELSE 0
             END AS bit) as Saleable, *
FROM Product

You only need to use the CAST operator if you want the result as a Boolean value. If you are happy with an int, this works:

SELECT CASE
            WHEN Obsolete = 'N' or InStock = 'Y'
               THEN 1
               ELSE 0
       END as Saleable, *
FROM Product

CASE statements can be embedded in other CASE statements and even included in aggregates.

SQL Server Denali (SQL Server 2012) adds the IIF statement which is also available in access (pointed out by Martin Smith):

SELECT IIF(Obsolete = 'N' or InStock = 'Y', 1, 0) as Saleable, * FROM Product
user_68190

The case statement is your friend in this situation, and takes one of two forms:

The simple case:

SELECT CASE <variable> WHEN <value>      THEN <returnvalue>
                       WHEN <othervalue> THEN <returnthis>
                                         ELSE <returndefaultcase>
       END AS <newcolumnname>
FROM <table>

The extended case:

SELECT CASE WHEN <test>      THEN <returnvalue>
            WHEN <othertest> THEN <returnthis>
                             ELSE <returndefaultcase>
       END AS <newcolumnname>
FROM <table>

You can even put case statements in an order by clause for really fancy ordering.

Jonathan_69100

You can find some nice examples in The Power of SQL CASE Statements, and I think the statement that you can use will be something like this (from 4guysfromrolla):

SELECT
    FirstName, LastName,
    Salary, DOB,
    CASE Gender
        WHEN 'M' THEN 'Male'
        WHEN 'F' THEN 'Female'
    END
FROM Employees
Sven_460

Use CASE. Something like this.

SELECT Salable =
        CASE Obsolete
        WHEN 'N' THEN 1
        ELSE 0
    END
user_3120 
SELECT  
(CASE 
     WHEN (Obsolete = 'N' OR InStock = 'Y') THEN 'YES'
                                            ELSE 'NO' 
 END) as Salable
, * 
FROM Product
John_Sheehan_17860

Microsoft SQL Server (T-SQL)

In a select, use:

select case when Obsolete = 'N' or InStock = 'Y' then 'YES' else 'NO' end

In a where clause, use:

where 1 = case when Obsolete = 'N' or InStock = 'Y' then 1 else 0 end
user_76580

From this link, we can understand IF THEN ELSE in T-SQL:

IF EXISTS(SELECT *
          FROM   Northwind.dbo.Customers
          WHERE  CustomerId = 'ALFKI')
  PRINT 'Need to update Customer Record ALFKI'
ELSE
  PRINT 'Need to add Customer Record ALFKI'

IF EXISTS(SELECT *
          FROM   Northwind.dbo.Customers
          WHERE  CustomerId = 'LARSE')
  PRINT 'Need to update Customer Record LARSE'
ELSE
  PRINT 'Need to add Customer Record LARSE'

Isn't this good enough for T-SQL?

user_2443850 
 SELECT
   CASE 
      WHEN OBSOLETE = 'N' or InStock = 'Y' THEN 'TRUE' 
      ELSE 'FALSE' 
   END AS Salable,
   * 
FROM PRODUCT
santiiiii_65470

Use a CASE statement:

SELECT CASE
       WHEN (Obsolete = 'N' OR InStock = 'Y')
       THEN 'Y'
       ELSE 'N'
END as Available

etc...
Admin1

As an alternative solution to the CASE statement, a table-driven approach can be used:

DECLARE @Product TABLE (ID INT, Obsolete VARCHAR(10), InStock VARCHAR(10))
INSERT INTO @Product VALUES
(1,'N','Y'),
(2,'A','B'),
(3,'N','B'),
(4,'A','Y')

SELECT P.* , ISNULL(Stmt.Saleable,0) Saleable
FROM
    @Product P
    LEFT JOIN
        ( VALUES
            ( 'N', 'Y', 1 )
        ) Stmt (Obsolete, InStock, Saleable)
        ON  P.InStock = Stmt.InStock OR P.Obsolete = Stmt.Obsolete

Result:

ID          Obsolete   InStock    Saleable
----------- ---------- ---------- -----------
1           N          Y          1
2           A          B          0
3           N          B          1
4           A          Y          1
user_85001100

You can have two choices for this to actually implement:

  1. Using IIF, which got introduced from SQL Server 2012:

    SELECT IIF ( (Obsolete = 'N' OR InStock = 'Y'), 1, 0) AS Saleable, * FROM Product

  2. Using Select Case:

    SELECT CASE
    WHEN Obsolete = 'N' or InStock = 'Y'
        THEN 1
        ELSE 0
    END as Saleable, *
    FROM Product
Admin1 
SELECT
if((obsolete = 'N' OR instock = 'Y'), 1, 0) AS saleable, *
FROM
product;
user_102380860

Question:

SELECT IF(Obsolete = 'N' OR InStock = 'Y' ? 1 : 0) AS Saleable, * FROM Product

ANSI:

Select 
  case when p.Obsolete = 'N' 
  or p.InStock = 'Y' then 1 else 0 end as Saleable, 
  p.* 
FROM 
  Product p;

Using aliases -- p in this case -- will help prevent issues.

user_105883020

Using SQL CASE is just like normal If / Else statements. In the below query, if obsolete value = 'N' or if InStock value = 'Y' then the output will be 1. Otherwise the output will be 0. Then we put that 0 or 1 value under the Salable Column.

SELECT
      CASE
           WHEN obsolete = 'N' OR InStock = 'Y'
          THEN 1
        ELSE 0
      END AS Salable
      , *
FROM PRODUCT
user_129101570

It will be something like that:

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;
user_39019440

I like the use of the CASE statements, but the question asked for an IF statement in the SQL Select. What I've used in the past has been:

SELECT

   if(GENDER = "M","Male","Female") as Gender

FROM ...

It's like the Excel or sheets IF statements where there is a conditional followed by the true condition and then the false condition:

if(condition, true, false)

Furthermore, you can nest the if statements (but then use should use a CASE :-)

(Note: this works in MySQL Workbench, but it may not work on other platforms)

user_120467870 
SELECT 
  CAST(
    CASE WHEN Obsolete = 'N' 
    or InStock = 'Y' THEN ELSE 0 END AS bit
  ) as Saleable, * 
FROM 
  Product
user_98224220

For the sake of completeness, I would add that SQL uses three-valued logic. The expression:

obsolete = 'N' OR instock = 'Y'

Could produce three distinct results:

| obsolete | instock | saleable |
|----------|---------|----------|
| Y        | Y       | true     |
| Y        | N       | false    |
| Y        | null    | null     |
| N        | Y       | true     |
| N        | N       | true     |
| N        | null    | true     |
| null     | Y       | true     |
| null     | N       | null     |
| null     | null    | null     |

So for example if a product is obsolete but you dont know if product is instock then you dont know if product is saleable. You can write this three-valued logic as follows:

SELECT CASE
           WHEN obsolete = 'N' OR instock = 'Y' THEN 'true'
           WHEN NOT (obsolete = 'N' OR instock = 'Y') THEN 'false'
           ELSE NULL
       END AS saleable

Once you figure out how it works, you can convert three results to two results by deciding the behavior of null. E.g. this would treat null as not saleable:

SELECT CASE
           WHEN obsolete = 'N' OR instock = 'Y' THEN 'true'
           ELSE 'false' -- either false or null
       END AS saleable
user_870150

You can use a case statement:

Select
Case WHEN (Obsolete = 'N' or InStock = 'Y') THEN 1 ELSE 0 END Saleable,
Product.*
from Product
user_86929570

There are multiple conditions.

SELECT

(CASE
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1001' THEN 'DM'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1002' THEN 'GS'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1003' THEN 'MB'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1004' THEN 'MP'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1005' THEN 'PL'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1008' THEN 'DM-27'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1011' THEN 'PB'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1012' THEN 'UT-2'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1013' THEN 'JGC'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1014' THEN 'SB'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1015' THEN 'IR'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1016' THEN 'UT-3'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1017' THEN 'UT-4'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1019' THEN 'KR'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1020' THEN 'SYB-SB'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1021' THEN 'GR'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1022' THEN 'SYB-KP'
WHEN RIGHT((LEFT(POSID,5)),4) LIKE '1026' THEN 'BNS'

  ELSE ''
END) AS OUTLET

FROM matrixcrm.Transact
user_15497830

You can find some nice examples in https://spikeslot.com/guides-and-tricks/ca, and I think the statement that you can use will be something like this (from spikeslot.com/ca):

SELECT
    FirstName, LastName,
    Salary, DOB,
    CASE Gender
        WHEN 'M' THEN 'Male'
        WHEN 'F' THEN 'Female'
    END
FROM Employees
user_71824970
Related