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

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33 Answers

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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

9

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.

5

From SQL Server 2012 you can use the IIF function for this.

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

This is effectively just a shorthand (albeit not standard SQL) way of writing CASE.

I prefer the conciseness when compared with the expanded CASE version.

Both IIF() and CASE resolve as expressions within a SQL statement and can only be used in well-defined places.

The CASE expression cannot be used to control the flow of execution of Transact-SQL statements, statement blocks, user-defined functions, and stored procedures.

If your needs can not be satisfied by these limitations (for example, a need to return differently shaped result sets dependent on some condition) then SQL Server does also have a procedural IF keyword.

IF @IncludeExtendedInformation = 1 BEGIN SELECT A,B,C,X,Y,Z FROM T END
ELSE BEGIN SELECT A,B,C FROM T END

Care must sometimes be taken to avoid parameter sniffing issues with this approach however.

1

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

2

Use CASE. Something like this.

SELECT Salable = CASE Obsolete WHEN 'N' THEN 1 ELSE 0 END

0

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

0

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

1

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?

2

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

0

Simple if-else statement in SQL Server:

DECLARE @val INT;
SET @val = 15;
IF @val < 25
PRINT 'Hi Ravi Anand';
ELSE
PRINT 'By Ravi Anand.';
GO

Nested If...else statement in SQL Server -

DECLARE @val INT;
SET @val = 15;
IF @val < 25
PRINT 'Hi Ravi Anand.';
ELSE
BEGIN
IF @val < 50 PRINT 'what''s up?';
ELSE PRINT 'Bye Ravi Anand.';
END;
GO

1

Use a CASE statement:

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

A new feature, IIF (that we can simply use), was added in SQL Server 2012:

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

3

Use pure bit logic:

DECLARE @Product TABLE ( id INT PRIMARY KEY IDENTITY NOT NULL ,Obsolote CHAR(1) ,Instock CHAR(1)
)
INSERT INTO @Product ([Obsolote], [Instock]) VALUES ('N', 'N'), ('N', 'Y'), ('Y', 'Y'), ('Y', 'N')
;
WITH cte
AS
( SELECT 'CheckIfInstock' = CAST(ISNULL(NULLIF(ISNULL(NULLIF(p.[Instock], 'Y'), 1), 'N'), 0) AS BIT) ,'CheckIfObsolote' = CAST(ISNULL(NULLIF(ISNULL(NULLIF(p.[Obsolote], 'N'), 0), 'Y'), 1) AS BIT) ,* FROM @Product AS p
)
SELECT 'Salable' = c.[CheckIfInstock] & ~c.[CheckIfObsolote] ,*
FROM [cte] c

See working demo: if then without case in SQL Server.

For start, you need to work out the value of true and false for selected conditions. Here comes two NULLIF:

for true: ISNULL(NULLIF(p.[Instock], 'Y'), 1)
for false: ISNULL(NULLIF(p.[Instock], 'N'), 0)

combined together gives 1 or 0. Next use bitwise operators.

It's the most WYSIWYG method.

6

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' )

SELECT CASE WHEN profile.nrefillno = 0 THEN 'N' ELSE 'R'END as newref
From profile

0

case statement some what similar to if in SQL server
SELECT CASE WHEN Obsolete = 'N' or InStock = 'Y' THEN 1 ELSE 0 END as Saleable, *
FROM Product

2

This isn't an answer, just an example of a CASE statement in use where I work. It has a nested CASE statement. Now you know why my eyes are crossed.

 CASE orweb2.dbo.Inventory.RegulatingAgencyName WHEN 'Region 1' THEN orweb2.dbo.CountyStateAgContactInfo.ContactState WHEN 'Region 2' THEN orweb2.dbo.CountyStateAgContactInfo.ContactState WHEN 'Region 3' THEN orweb2.dbo.CountyStateAgContactInfo.ContactState WHEN 'DEPT OF AGRICULTURE' THEN orweb2.dbo.CountyStateAgContactInfo.ContactAg ELSE ( CASE orweb2.dbo.CountyStateAgContactInfo.IsContract WHEN 1 THEN orweb2.dbo.CountyStateAgContactInfo.ContactCounty ELSE orweb2.dbo.CountyStateAgContactInfo.ContactState END ) END AS [County Contact Name]

3

If you're inserting results into a table for the first time, rather than transferring results from one table to another, this works in Oracle 11.2g:

INSERT INTO customers (last_name, first_name, city) SELECT 'Doe', 'John', 'Chicago' FROM dual WHERE NOT EXISTS (SELECT '1' from customers where last_name = 'Doe' and first_name = 'John' and city = 'Chicago');

1

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

2

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

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

For those who uses SQL Server 2012, IIF is a feature that has been added and works as an alternative to Case statements.

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

1

SELECT
if((obsolete = 'N' OR instock = 'Y'), 1, 0) AS saleable, *
FROM
product;

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

3

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.

Using SQL CASE is just like normal If / Else statements. In below query, If obsolete value = 'N' or If InStock value = 'Y' Then Output will be 1. Otherwise 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

2

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;

1

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 MySQLWorkbench but may not work in other platforms)

1

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

2

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

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