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Logical Functions - CHOOSE (Transact-SQL)

  • Статия

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance

Returns the item at the specified index from a list of values in SQL Server.

Transact-SQL syntax conventions

Syntax

CHOOSE ( index, val_1, val_2 [, val_n ] )

Arguments

index

Is an integer expression that represents a 1-based index into the list of the items following it.

If the provided index value has a numeric data type other than int, then the value is implicitly converted to an integer. If the index value exceeds the bounds of the array of values, then CHOOSE returns null.

val_1 ... val_n

List of comma separated values of any data type.

Return Types

Returns the data type with the highest precedence from the set of types passed to the function. For more information, see Data Type Precedence (Transact-SQL).

Remarks

CHOOSE acts like an index into an array, where the array is composed of the arguments that follow the index argument. The index argument determines which of the following values will be returned.

Examples

A. Simple CHOOSE example

The following example returns the third item from the list of values that is provided.

SELECT CHOOSE ( 3, 'Manager', 'Director', 'Developer', 'Tester' ) AS Result;

Here's the result set.

Result  
-------------  
Developer  
  
(1 row(s) affected)

B. Simple CHOOSE example based on column

The following example returns a simple character string based on the value in the ProductCategoryID column.

USE AdventureWorks2022;  
GO  
SELECT ProductCategoryID, CHOOSE (ProductCategoryID, 'A','B','C','D','E') AS Expression1  
FROM Production.ProductCategory;

Here's the result set.

ProductCategoryID Expression1  
----------------- -----------  
3                 C  
1                 A  
2                 B  
4                 D  
  
(4 row(s) affected)

C. CHOOSE in combination with MONTH

The following example returns the season in which a product model was last modified. The MONTH function is used to return the month value from the column ModifiedDate. The CHOOSE function is used to assign a Northern Hemisphere season. This sample uses the AdventureWorksLT database, which can be quickly installed as the sample database for a new Azure SQL Database. For more information, see AdventureWorks sample databases.

SELECT Name, ModifiedDate, 
CHOOSE(MONTH(ModifiedDate),'Winter','Winter', 'Spring','Spring','Spring','Summer','Summer',   
                          'Summer','Autumn','Autumn','Autumn','Winter') AS Quarter_Modified
FROM SalesLT.ProductModel AS PM
WHERE Name LIKE '%Frame%'
ORDER BY ModifiedDate;

Here's the result set.

Name                        ModifiedDate            Quarter_Modified
--------------------------- ----------------------- ----------------
HL Road Frame               2002-05-02 00:00:00.000 Spring
HL Mountain Frame           2005-06-01 00:00:00.000 Summer
LL Road Frame               2005-06-01 00:00:00.000 Summer
ML Road Frame               2005-06-01 00:00:00.000 Summer
ML Road Frame-W             2006-06-01 00:00:00.000 Summer
ML Mountain Frame           2006-06-01 00:00:00.000 Summer
ML Mountain Frame-W         2006-06-01 00:00:00.000 Summer
LL Mountain Frame           2006-11-20 09:56:38.273 Autumn
HL Touring Frame            2009-05-16 16:34:28.980 Spring
LL Touring Frame            2009-05-16 16:34:28.980 Spring

(10 rows affected)

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