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我正在尝试创建一个查询，该查询将在视图中获取多列并将其放入查询中的一列。每列的值需要用“|”分隔 （管道）。

我试过了：

1) (expression1 + '|' + expression2) AS xxxx，但如果一个表达式有一个空值，它使结果为“空”。

2) CAST (expression1 as varchar (10)) + '|' + CAST (expression2 as varchar (10)) AS xxxx，但得到相同的结果。

3) CASE (expression1 is null) then (' ') else (expression1) +'|' + CASE (expression2 is null) then (' ') else (expression2) END AS xxxx，但在关键字附近出现语法错误'AS'.

这是使用 CASE 的完整查询。

SELECT DISTINCT dbo.REG.BUILDING, dbo.REG.CURRENT_STATUS, dbo.REG_CONTACT.LOGIN_ID, dbo.REG.LAST_NAME
, CASE WHEN dbo.View_MYAccess_Period1.CRSGRP1 is null then ' ' else        dbo.View_MYAccess_Period1.CRSGRP1 + ' |' +
  CASE WHEN dbo.View_MYAccess_Period2.CRSGRP2 is null then ' ' else dbo.View_MYAccess_Period2.CRSGRP2
END AS CRSGRP

FROM  dbo.REG_CONTACT RIGHT OUTER JOIN
dbo.REG_STU_CONTACT ON dbo.REG_CONTACT.CONTACT_ID = dbo.REG_STU_CONTACT.CONTACT_ID RIGHT OUTER JOIN 
dbo.REG ON dbo.REG_STU_CONTACT.STUDENT_ID = dbo.REG.STUDENT_ID LEFT OUTER JOIN 
dbo.View_MYAccess_Period1 ON dbo.REG.STUDENT_ID = dbo.View_MYAccess_Period1.STUDENT_ID LEFT OUTER JOIN
dbo.View_MYAccess_Period2 ON dbo.REG.STUDENT_ID = dbo.View_MYAccess_Period2.STUDENT_ID

对这个新手的任何帮助将不胜感激！

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2 回答 2

1

使用 ISNULL 函数，

SELECT DISTINCT dbo.REG.BUILDING, dbo.REG.CURRENT_STATUS, dbo.REG_CONTACT.LOGIN_ID, dbo.REG.LAST_NAME
, ISNULL(dbo.View_MYAccess_Period1.CRSGRP1,' ') + ' |' +
  ISNULL(dbo.View_MYAccess_Period2.CRSGRP2,' ') CRSGRP

FROM  dbo.REG_CONTACT RIGHT OUTER JOIN
dbo.REG_STU_CONTACT ON dbo.REG_CONTACT.CONTACT_ID = dbo.REG_STU_CONTACT.CONTACT_ID RIGHT OUTER JOIN 
dbo.REG ON dbo.REG_STU_CONTACT.STUDENT_ID = dbo.REG.STUDENT_ID LEFT OUTER JOIN 
dbo.View_MYAccess_Period1 ON dbo.REG.STUDENT_ID = dbo.View_MYAccess_Period1.STUDENT_ID LEFT OUTER JOIN
dbo.View_MYAccess_Period2 ON dbo.REG.STUDENT_ID = dbo.View_MYAccess_Period2.STUDENT_ID
于 2013-09-18T18:32:39.477 回答
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在示例 1 中，如果表达式为空，您可以使用该COALESCE(expression, fallback)函数强制expression返回一个回退值。（然后相应地调整其余的逻辑。）

在您的示例 3 中，您需要另一个END关键字：

CASE
    (expression1 is null) then (' ')
    ELSE (expression1) +'|' +
        CASE (expression2 is null) then (' ') else (expression2) END
END AS xxxx
于 2013-09-18T18:32:08.117 回答