经典的多语句表值函数

set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go

CREATE FUNCTION [dbo].[ufnGetContactInformation](@ContactID int)
RETURNS @retContactInformation TABLE
(
    -- Columns returned by the function
    [ContactID] int PRIMARY KEY NOT NULL,
    [FirstName] [nvarchar](50) NULL,
    [LastName] [nvarchar](50) NULL,
    [JobTitle] [nvarchar](50) NULL,
    [ContactType] [nvarchar](50) NULL
)
AS
-- Returns the first name, last name, job title and contact type for the specified contact.
BEGIN
    DECLARE
        @FirstName [nvarchar](50),
        @LastName [nvarchar](50),
        @JobTitle [nvarchar](50),
        @ContactType [nvarchar](50);

    -- Get common contact information
    SELECT
        @ContactID = ContactID,
        @FirstName = FirstName,
        @LastName = LastName
    FROM [Person].[Contact]
    WHERE [ContactID] = @ContactID;

    SET @JobTitle =
        CASE
            -- Check for employee
            WHEN EXISTS(SELECT * FROM [HumanResources].[Employee] e
                WHERE e.[ContactID] = @ContactID)
                THEN (SELECT [Title]
                    FROM [HumanResources].[Employee]
                    WHERE [ContactID] = @ContactID)

            -- Check for vendor
            WHEN EXISTS(SELECT * FROM [Purchasing].[VendorContact] vc
                    INNER JOIN [Person].[ContactType] ct
                    ON vc.[ContactTypeID] = ct.[ContactTypeID]
                WHERE vc.[ContactID] = @ContactID)
                THEN (SELECT ct.[Name]
                    FROM [Purchasing].[VendorContact] vc
                        INNER JOIN [Person].[ContactType] ct
                        ON vc.[ContactTypeID] = ct.[ContactTypeID]
                    WHERE vc.[ContactID] = @ContactID)

            -- Check for store
            WHEN EXISTS(SELECT * FROM [Sales].[StoreContact] sc
                    INNER JOIN [Person].[ContactType] ct
                    ON sc.[ContactTypeID] = ct.[ContactTypeID]
                WHERE sc.[ContactID] = @ContactID)
                THEN (SELECT ct.[Name]
                    FROM [Sales].[StoreContact] sc
                        INNER JOIN [Person].[ContactType] ct
                        ON sc.[ContactTypeID] = ct.[ContactTypeID]
                    WHERE [ContactID] = @ContactID)

            ELSE NULL
        END;

    SET @ContactType =
        CASE
            -- Check for employee
            WHEN EXISTS(SELECT * FROM [HumanResources].[Employee] e
                WHERE e.[ContactID] = @ContactID)
                THEN 'Employee'

            -- Check for vendor
            WHEN EXISTS(SELECT * FROM [Purchasing].[VendorContact] vc
                    INNER JOIN [Person].[ContactType] ct
                    ON vc.[ContactTypeID] = ct.[ContactTypeID]
                WHERE vc.[ContactID] = @ContactID)
                THEN 'Vendor Contact'

            -- Check for store
            WHEN EXISTS(SELECT * FROM [Sales].[StoreContact] sc
                    INNER JOIN [Person].[ContactType] ct
                    ON sc.[ContactTypeID] = ct.[ContactTypeID]
                WHERE sc.[ContactID] = @ContactID)
                THEN 'Store Contact'

            -- Check for individual consumer
            WHEN EXISTS(SELECT * FROM [Sales].[Individual] i
                WHERE i.[ContactID] = @ContactID)
                THEN 'Consumer'
        END;

    -- Return the information to the caller
    IF @ContactID IS NOT NULL
    BEGIN
        INSERT @retContactInformation
        SELECT @ContactID, @FirstName, @LastName, @JobTitle, @ContactType;
    END;

    RETURN;
END;