SQL 查询中case的运用

适用场景： 需要根据现有字段经过一定条件得到新的查询字段
相关语法： CASE WHEN 条件1 TEHN 结果1 WHEN 条件2 THEN 结果2 ...... ELSE 结果N END

练习代码：

 1 SELECT  * ,
 2             ( '评分: <span style=''font-weight:bold''>' + INFO.CMScore + '</span><br/>评级: <span style=''font-weight:bold''>' + INFO.CMGrade+'</span>' ) AS CMEvaluate ,
 3             ( '评分: <span style=''font-weight:bold''>' + INFO.ExamScore + '</span><br/>评级: <span style=''font-weight:bold''>' + INFO.ExamGrade+'</span>' ) AS ExamEvaluate
 4     FROM    ( SELECT    dbo.LB_Project.LB_Pro_ID ,  dbo.LB_Project.BD_ID ,  LB_Project.LB_Pro_Code ,
 5            -- ISNULL((SELECT TOP 1 Emp_Name FROM dbo.IC_Employee WHERE Emp_ID=dbo.LB_Porject_ScoreCard.Emp_ID_Report),'- -') AS ReportEmp, 
 6            -- ISNULL((SELECT TOP 1 Emp_Name FROM dbo.IC_Employee WHERE Emp_ID=dbo.LB_Porject_ScoreCard.Emp_ID_Exam),'- -') AS ExamEmp, 
 7             (SELECT TOP 1  BDName   FROM  dbo.Busi_Definition  WHERE  BD_ID = dbo.LB_Project.BD_ID ) AS BDName ,
 8             (SELECT TOP 1  BDCode   FROM  dbo.Busi_Definition  WHERE  BD_ID = dbo.LB_Project.BD_ID ) AS BDCode ,
 9             dbo.LB_Project.Cust_ID ,
10             (SELECT TOP 1  Cust_Name  FROM  dbo.Cust_Main  WHERE  Cust_ID = dbo.LB_Project.Cust_ID) AS CustName ,
11             (SELECT TOP 1  IDCard  FROM dbo.Cust_Main   WHERE  Cust_ID = dbo.LB_Project.Cust_ID) AS CustIDCard ,
12              --dbo.LB_Project.Dept_ID ,
13             (SELECT TOP 1  Dept_Name FROM  dbo.IC_Departments WHERE  Dept_ID = LB_Project.Dept_ID) AS DeptName ,
14             dbo.LB_Project.Emp_ID_ZB ,
15             (SELECT TOP 1 Emp_Name FROM dbo.IC_Employee WHERE  Emp_ID = LB_Project.Emp_ID_ZB ) AS EmpName_ZB ,
16              dbo.LB_Project.Emp_ID_XB ,
17             (SELECT TOP 1 Emp_Name FROM  dbo.IC_Employee  WHERE Emp_ID = LB_Project.Emp_ID_XB ) AS EmpName_XB ,
18              dbo.LB_Project.LoanAmount , 
19              --dbo.LB_Project.TermValue , 
20              --dbo.LB_Project.LoanUses , 
21              --dbo.LB_Project.TermUnit ,
22             (CAST(TermValue AS NVARCHAR(10)) + ( CASE TermUnit  WHEN '月' THEN '个' + TermUnit ELSE TermUnit END ) ) AS Term ,
23             (CAST(CAST(RateValue AS DECIMAL(6,2)) AS NVARCHAR(10)) + '%/' + RateUnit ) AS Rate ,
24             --dbo.LB_Project.RateValue ,   dbo.LB_Project.RateUnit ,  dbo.LB_Project.RM_ID ,
25             (SELECT TOP 1 RM_Name FROM  dbo.Set_RepayMent WHERE  RM_ID = LB_Project.RM_ID) AS RMName ,
26             --dbo.LB_Project.GM_ID ,
27             (SELECT '['+GM_Name+']'  FROM  dbo.Set_GuaranteeMethod WHERE  GM_ID IN (SELECT Value FROM dbo.SplitString(LB_Project.GM_ID,',',1) ) FOR XML PATH('')) AS GMName ,
28              --dbo.LB_Project.VerifyStatus ,
29             dbo.LB_Project.CreateTime , 
30             dbo.LB_Project.Status ,
31             (CASE dbo.LB_Project.Status WHEN 0 THEN '待确认'  WHEN 1 THEN '待复核'   WHEN 2 THEN '已评分' ELSE '- -' END ) StatusName ,
32             --dbo.LB_Project_JRWPFD.LB_Pro_JP_ID ,
33             --dbo.LB_Project_JRWPFD.MM_ID ,
34             (CASE WHEN EXISTS(SELECT 1 FROM dbo.Busi_Definition WHERE BD_ID=dbo.LB_Project.BD_ID AND  BDCode='BD_CODE_JRWPFD') 
35              THEN (SELECT TOP 1  MM_Name FROM dbo.Market_Main  WHERE   MM_ID = LB_Project_JRWPFD.MM_ID)
36              WHEN EXISTS(SELECT 1 FROM dbo.Busi_Definition WHERE BD_ID=dbo.LB_Project.BD_ID AND  BDCode='BD_CODE_ZHLGCYD')
37              THEN (SELECT TOP 1 MarketName FROM dbo.LB_Project_ZHLGCYD) ELSE '- -' END ) AS MMName ,
38              --dbo.LB_Project_JRWPFD.S_BC_ID ,
39             (CASE WHEN EXISTS(SELECT 1 FROM dbo.Busi_Definition WHERE BD_ID=dbo.LB_Project.BD_ID AND  BDCode='BD_CODE_JRWPFD') 
40             THEN (SELECT TOP 1  Name FROM  dbo.Set_BusinessCategory  WHERE   S_BC_ID = dbo.LB_Project_JRWPFD.S_BC_ID)   
41             WHEN EXISTS(SELECT 1 FROM dbo.Busi_Definition WHERE BD_ID=dbo.LB_Project.BD_ID AND  BDCode='BD_CODE_ZHLGCYD') 
42             THEN (SELECT TOP 1 CategoryArea FROM dbo.LB_Project_ZHLGCYD) ELSE '- -' END) AS CateGoryName ,
43            --dbo.LB_Project_JRWPFD.Paving ,
44            --dbo.LB_Project_JRWPFD.ValuationDetail ,
45           --dbo.LB_Project_JRWPFD.Valuation ,
46           (CASE WHEN dbo.LB_Project.Status = 2  THEN CONVERT(NVARCHAR(10), dbo.LB_Porject_ScoreCard.ExamScore)  
              ELSE '- -'  END ) AS ExamScore ,
47            (CASE WHEN LB_Porject_ScoreCard.Status = 2  THEN ISNULL(( SELECT TOP 1  GSName FROM  ( SELECT  GSName FROM    dbo.SC_GradeStandard 
48             WHERE Status = 0 AND LB_Porject_ScoreCard.ExamScore BETWEEN MinValue AND  MaxValue AND SC_ID = dbo.LB_Porject_ScoreCard.SC_ID) INFO
49             WHERE INFO.GSName <> '' ), '- -') ELSE '- -' END ) AS ExamGrade ,
50            (CASE WHEN dbo.LB_Project.Status > 0  THEN CONVERT(NVARCHAR(10), dbo.LB_Porject_ScoreCard.ReportScore) ELSE '- -' END ) AS CMScore ,
51            (CASE WHEN LB_Porject_ScoreCard.Status > 0 THEN ISNULL(( SELECT TOP 1 GSName FROM  ( SELECT  GSName FROM  dbo.SC_GradeStandard
52             WHERE Status = 0  AND LB_Porject_ScoreCard.ReportScore BETWEEN MinValue AND  MaxValue AND SC_ID = dbo.LB_Porject_ScoreCard.SC_ID) INFO
53             WHERE INFO.GSName <> '' ), '- -') ELSE '- -' END ) AS CMGrade  FROM      dbo.LB_Project
54             LEFT JOIN dbo.LB_Porject_ScoreCard ON LB_Porject_ScoreCard.LB_Pro_ID = LB_Project.LB_Pro_ID
55             LEFT OUTER JOIN dbo.LB_Project_JRWPFD ON dbo.LB_Project_JRWPFD.LB_Pro_ID = dbo.LB_Project.LB_Pro_ID 
56             LEFT JOIN dbo.LB_Project_ZHLGCYD ON LB_Project_ZHLGCYD.LB_Pro_ID = LB_Project.LB_Pro_ID) INFO;

__EOF__

本文作者：DaiWK
本文链接：https://www.cnblogs.com/daiwk/p/10563357.html
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