Wie führe ich ein IF...THEN in einem SQL SELECT aus?

Question

Wie führe ich eine IF...THEN in einem SQL SELECT Aussage?

Zum Beispiel:

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

Answer 1

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

Answer 2

Desde dieser Link können wir verstehen 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' 

Ist das nicht gut genug für T-SQL?

Answer 3

Microsoft SQL Server (T-SQL)

In einem select verwenden:

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

In einem where Klausel, verwenden:

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

Answer 4

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

Answer 5

Einfache if-else-Anweisung in SQL Server:

DECLARE @val INT;
SET @val = 15;

IF @val < 25
PRINT 'Hi Ravi Anand';
ELSE
PRINT 'By Ravi Anand.';

GO

Verschachtelte If...else-Anweisung 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