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sqlsql-servert-sqlif-statementcase
Eric Labashosky
Eric Labashosky

Reputation: 29981

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

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

Upvotes: 1804

Views: 4724689

Answers (30)

tunnelview
tunnelview

Reputation: 47

Looks like an old question, however if I understood your question and thought correctly, you want to implement the if/else conditional statement in SQL. Both are calculated as a separate column.

The iif() function was introduced in 2012, however let's understand the difference between case and iif() statements. If you need to write just one condition, then iif() is sufficient, however if you want to write multiple iif() conditions within one statement then you will have to use `case' statement as demonstrated in above responses. Here is an example for your reference.

   `select 
    s.name,s.mrn, 
    s.specialtyshort,
    s.admissiondate, 
    s.dischargedate,
    iif(s.admissiondate is not null, 'linked','notlinked') as s.admissionStatus 
    from specialty s`

Now if you need to include any other filter or condition in the above statement, you will need to write another iif() statement. On the other hand, case expression can include multiple conditions within one expression. Do some research on the difference between a case statement and case expression. The below is a case expression that evaluates to a value.

`select
 t.name 
,t.MRID
,t.operationDate
,t.dischargeDate
,case 
     when t.specialty like '%obstetrics%' then 'OBS'
     when t.specialty like '%orthopaedics%' then 'ORT'
     when t.specialty like '%General Surgery%' then 'GEN'
     when t.specialty like '%Cardiology%' then 'CAR'
else 'not available' --evaluates to a value.
end as derived_specialty

from 
OperationsTables t`

Upvotes: 1

Serkan Arslan
Serkan Arslan

Reputation: 13403

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

Upvotes: 10

Robert B. Grossman
Robert B. Grossman

Reputation: 157

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');

Upvotes: 10

Tharuka Madumal
Tharuka Madumal

Reputation: 201

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

Upvotes: 8

Prashant Marathay
Prashant Marathay

Reputation: 313

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)

Upvotes: 4

sven
sven

Reputation: 18368

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

Upvotes: 116

Durlove Roy
Durlove Roy

Reputation: 217

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

Upvotes: 0

Darrel Miller
Darrel Miller

Reputation: 142222

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

Upvotes: 2054

yusuf hayırsever
yusuf hayırsever

Reputation: 701

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

Upvotes: 5

Salman Arshad
Salman Arshad

Reputation: 272316

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

Upvotes: 3

Muhammad Awais
Muhammad Awais

Reputation: 4502

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;

Upvotes: 3

user11127093
user11127093

Reputation:

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

Upvotes: 8

Ravi Anand
Ravi Anand

Reputation: 5534

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

Upvotes: 34

Tomasito
Tomasito

Reputation: 1883

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.

Upvotes: 23

Martin Smith
Martin Smith

Reputation: 453727

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.

Upvotes: 322

Ken
Ken

Reputation: 2838

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?

Upvotes: 52

user7658
user7658

Reputation: 952

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

Upvotes: 51

David Cohn
David Cohn

Reputation: 79

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.

Upvotes: 5

sandeep rawat
sandeep rawat

Reputation: 4957

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

Upvotes: 24

user8422856
user8422856

Reputation: 

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

Upvotes: 9

Christopher
Christopher

Reputation:

Use a CASE statement:

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

etc...

Upvotes: 25

JustJohn
JustJohn

Reputation: 1460

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]

Upvotes: 13

onedaywhen
onedaywhen

Reputation: 57073

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' )

Upvotes: 18

Chanukya
Chanukya

Reputation: 5893

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

Upvotes: 13

Jonathan
Jonathan

Reputation: 26639

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.

Upvotes: 371

Mohammad Atiour Islam
Mohammad Atiour Islam

Reputation: 5708

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

Upvotes: 16

Dibin
Dibin

Reputation: 1578

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

Upvotes: 4

John Sheehan
John Sheehan

Reputation: 78152

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

Upvotes: 64

Santiago Cepas
Santiago Cepas

Reputation: 4094

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

Upvotes: 52

palehorse
palehorse

Reputation: 27516

Use CASE. Something like this.

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

Upvotes: 87

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