SQL 中Case的用法

因为 根据需求要对查询出的数据情况进行按照条件显示，所以利用case来实现这个要点：

条件是如果名字为空且id为0，这个用户就是报价用户

　　　　如果是名字为空且id不为0，这个用户名字不存在

　　　　如果名字不为空，那么就显示此用户名

USE [xb_quotation_dev]
GO

/****** Object:  StoredProcedure [dbo].[usp_GetHistory_Original_Price]    Script Date: 02/08/2012 11:07:35 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

-- =============================================
-- Author:        <Author,,Name>
-- Create date: <2012-02-08>
-- Description:    <获得钢材，板材，线材，炉料 原报价>
--@typeid=1 代表钢材，板材，线材；@typeid=2 代表炉料
-- =============================================
CREATE PROCEDURE [dbo].[usp_GetHistory_Original_Price]
@StartDate    DATETIME,
@EndDate    DateTime,
@TypeId    INT
AS
BEGIN
    SET NOCOUNT ON;
        IF(@TypeId=1)
            BEGIN
                WITH tm AS(
                            SELECT CONVERT(VARCHAR(10),PriceDate,120) AS PriceDate,AdminUserId FROM MD_HistoryRawPrice 
                                WHERE  CONVERT(VARCHAR(10),PriceDate,120)>=CONVERT(VARCHAR(10),@StartDate,120)
                                AND CONVERT(VARCHAR(10),PriceDate,120)<=CONVERT(VARCHAR(10),@EndDate,120)
                                GROUP BY CONVERT(VARCHAR(10),PriceDate,120),AdminUserId
                        )
                SELECT tm.PriceDate,tm.AdminUserId,
                        CASE WHEN(m.J_TrueName is null and tm.AdminUserId=0)    THEN '报价系统'
                        WHEN (m.J_TrueName IS null and tm.AdminUserId<>0)    THEN '名字不存在'
                        ELSE m.J_TrueName 
                        END AS J_TrueName
                        FROM tm LEFT JOIN Member_Info m on tm.AdminUserId = m.UNID ORDER BY tm.PriceDate DESC            
            END
        ELSE
            BEGIN
                WITH tm AS(
                            SELECT CONVERT(VARCHAR(10),PriceDate,120) AS PriceDate,AdminUserId FROM charge_HistoryRawPrice 
                            WHERE  CONVERT(VARCHAR(10),PriceDate,120)>=CONVERT(VARCHAR(10),@StartDate,120) 
                            AND CONVERT(VARCHAR(10),PriceDate,120)<=CONVERT(VARCHAR(10), @EndDate,120) 
                            GROUP BY CONVERT(VARCHAR(10),PriceDate,120),AdminUserId
                            )
                SELECT tm.PriceDate,tm.AdminUserId,
                        CASE WHEN(m.J_TrueName is null and tm.AdminUserId=0)    THEN '报价系统'
                        WHEN (m.J_TrueName IS null and tm.AdminUserId<>0)    THEN '名字不存在'
                        ELSE m.J_TrueName 
                        END AS J_TrueName
                        FROM tm LEFT JOIN Member_Info m on tm.AdminUserId = m.UNID ORDER BY tm.PriceDate DESC
            END
END

GO