T-SQL Recipes之Customized Database Objects

The Problem

创建灵活自定义对象决非是一个简单的任务。比如HR想看每种工作职称在所有年限里面的入职累计情况

The Solution

我们一步一步来拆解吧：

• 获取入职年限的集合，如1999,2000,2001...etc
• 根据唯一值来统计每年的入职数量，当然是得用动态PIVOT
• 然后写进SP里面

示例1：获取年限集合

DECLARE @hire_date_years TABLE
    (
      hire_date_year NVARCHAR(50)
    );
INSERT  INTO @hire_date_years
        ( hire_date_year
        )
        SELECT DISTINCT
                DATEPART(YEAR, Employee.HireDate)
        FROM    HumanResources.Employee;

DECLARE @sql_yearlist NVARCHAR(MAX);

SELECT  @sql_yearlist = ISNULL(@sql_yearlist, '') + ','
        + QUOTENAME(hire_date_year)
FROM    @hire_date_years

SET @sql_yearlist = STUFF(@sql_yearlist, 1, 1, '')

SELECT  @sql_yearlist

示例2 根据唯一值来统计

DECLARE @hire_date_years TABLE
    (
      hire_date_year NVARCHAR(50)
    );
DECLARE @sql_yearlist NVARCHAR(MAX);
DECLARE @sql_command NVARCHAR(MAX);

INSERT  INTO @hire_date_years
        ( hire_date_year
        )
        SELECT DISTINCT
                DATEPART(YEAR, Employee.HireDate)
        FROM    HumanResources.Employee;

SELECT  @sql_yearlist = ISNULL(@sql_yearlist, '') + N','
        + QUOTENAME(hire_date_year)
FROM    @hire_date_years

SET @sql_yearlist = STUFF(@sql_yearlist, 1, 1, '')

SET @sql_command = N'
WITH    employee_data
          AS ( SELECT   Employee.BusinessEntityID ,
                        Employee.JobTitle ,
                        DATEPART(YEAR, Employee.HireDate) AS HireDate_Year
               FROM     HumanResources.Employee
             )

SELECT
        JobTitle,' + @sql_yearlist + N'
FROM    employee_data
PIVOT   (COUNT(BusinessEntityID) FOR HireDate_Year IN ('  + @sql_yearlist + N')) pivot_data'

PRINT @sql_command

示例3: 写进SP里面

IF OBJECT_ID(N'dbo.job_title_year_summary', 'P') IS NOT NULL
BEGIN
    DROP PROCEDURE dbo.job_title_year_summary;
END

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE PROCEDURE job_title_year_summary
AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    DECLARE @hire_date_years TABLE
        (
          hire_date_year NVARCHAR(50)
        );
    DECLARE @sql_yearlist NVARCHAR(MAX);
    DECLARE @sql_command NVARCHAR(MAX);

    INSERT  INTO @hire_date_years
            ( hire_date_year
            )
            SELECT DISTINCT
                    DATEPART(YEAR, Employee.HireDate)
            FROM    HumanResources.Employee;

    SELECT  @sql_yearlist = ISNULL(@sql_yearlist, '') + N','
            + QUOTENAME(hire_date_year)
    FROM    @hire_date_years

    SET @sql_yearlist = STUFF(@sql_yearlist, 1, 1, '')

    SET @sql_command = N'
    WITH    employee_data
              AS ( SELECT   Employee.BusinessEntityID ,
                            Employee.JobTitle ,
                            DATEPART(YEAR, Employee.HireDate) AS HireDate_Year
                   FROM     HumanResources.Employee
                 )

    SELECT
            JobTitle,' + @sql_yearlist + N'
    FROM    employee_data
    PIVOT   (COUNT(BusinessEntityID) FOR HireDate_Year IN ('  + @sql_yearlist + N')) pivot_data'

    PRINT @sql_command;
    EXEC sp_executesql @sql_command;
END
GO

有了这个存储过程，以后需要用它时，可以用昨时表来存储它的结果，做后一步的处理。