Execute Dynamic SQL commands in SQL Server

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In some applications having hard-coded SQL statements is not appealing, because of the dynamic nature of the queries being issued against the database server. Because of this sometimes there is a need to dynamically create a SQL statement on the fly and then run that command. This can be done quite simply from the application perspective where the statement is built on the fly whether you are using ASP.NET , ColdFusion or any other programming language. But how do you do this from within a SQL Server stored procedure? SQL Server offers a few ways of running a dynamically built SQL statement. These ways are: Writing a query with parameters Using EXEC Using sp_executesql Writing a query with parameters This first approach is pretty straightforward if you only need to pass parameters into the WHERE clause of your SQL statement. Let’s say we need to find all records from the Customers table where City = ‘London’. This can be done easily as the following example shows.
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SQL Case Statements

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SQL Case statement can be used in 2 forms:

  1. SQL Case statement with simple expression to compare and get results.
  2. SQL Case statement with search or comparison expression to get results.

1. SQL Case statement with simple expression:
You can use default Northwind Database to test the functionality and syntax of SQL case statement.





Syntax:

USE NORTHWIND

SELECT
'Title' =
CASE TITLEOFCOURTESY
WHEN 'MS.' THEN 'MISSUS'
WHEN 'MRS.' THEN 'MISTRESS'
WHEN 'MR.' THEN 'MISTER'
WHEN 'DR.' THEN 'DOCTOR'
ELSE ''
END,
TITLEOFCOURTESY,
FIRSTNAME,
LASTNAME
FROM EMPLOYEES



Output:

Title

TitleOfCourtsey

FirstName

LastName

Missus

Ms.

Nancy

Davolio

Doctor

Dr.

Andrew

Fuller

Missus

Ms.

Janet

Leverling

Mistress

Mrs.

Margaret

Peacock

Mister

Mr.

Steven

Buchanan

Mister

Mr.

Michael

Suyama

Mister

Mr.

Robert

King

Missus

Ms.

Laura

Callahan

Missus

Ms.

Anne

Dodsworth

2. SQL Case Statement with search comparison expressions:

Syntax:




USE NORTHWIND

SELECT
'COMMENT' =
CASE
WHEN  UNITPRICE IS NULL THEN 'NO PRICE DEFINED'
WHEN  UNITPRICE < 20 THEN 'LOW PRICE'
WHEN  UNITPRICE > 20 AND UNITPRICE < 30 THEN 'REASONABLE PRICE'
ELSE 'EXPENSIVE ITEM!!!'
END,
PRODUCTNAME,
UNITPRICE
FROM PRODUCTS

Output:


Comment

ProductName

UnitPrice

Low Price

Chai

18.00

Low Price

Chang

19.00

Low Price

Aniseed Syrup

10.00

Reasonable Price

Chef Anton's Cajun Seasoning

22.00

Reasonable Price

Chef Anton's Gumbo Mix

21.35

Reasonable Price

Grandma's Boysenberry Spread

25.00

Expensive Item!!!

Uncle Bob's Organic Dried Pears

30.00

Expensive Item!!!

Northwoods Cranberry Sauce

40.00

Comments

pravin mahit said…
can u tell me how to multiple case statement in one query?

thanks in advance
February 16, 2010 at 11:02 PM
Anonymous said…
Good one thanks!!

See this one too:

Searched case expression sql
September 9, 2013 at 12:20 AM
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