Question

我正在运行一个可能返回空行集的SQL查询。我想使用CASE语句处理它。

这是我尝试过的但是没有用

Case
When @@ROWCOUNT > 0 Then LTRIM(RTRIM(t.FirstName))  Else 'UNKNOWN'
End

case语句不返回任何值

如果我使用print @@ RowCount而不是Select我得到0值。

我该如何解决这个问题？

好的查询相当大，所以我会尝试解释它的作用。我在一个从HR数据库返回数据的函数中使用它。我需要员工信息，如姓名和工作任务。在某些情况下，我需要处理员工未知的数据。在那些情况下，我传递一个employeeId数为零。当我运行查询时，这会导致返回空。

我想要的是让函数将Name数据作为UNKNOWN返回。

希望这有助于清除请求

我已经修改了查询，因此我可以显示以下所有相关部分：

DECLARE @EID int = 0
DECLARE @AssignmentType varchar(max) = 'FirstName'
DECLARE @ReturnValue varchar(max)
DECLARE @EIDTemp TABLE(EID varchar(6), Section varchar(max), Division 
varchar(max), Bureau varchar(max), FirstName varchar(max), MiddleName 
varchar(max), LastName varchar(max));

Insert Into @EIDTemp
SELECT L1.Employee, P1.NAME As Section,
CASE 
    WHEN L1.DEPARTMENT IN (7010) THEN 'Legal Services Division' 
    WHEN L1.DEPARTMENT IN (7030,7040) THEN 'Fiscal Management Division'
    Else 'Other'
END AS Division,
CASE
    WHEN L1.DEPARTMENT IN (7130) THEN 'Administrative Services Bureau'
    ELSE ','
END As Bureau
,L1.FIRST_NAME
,L1.MIDDLE_NAME
,L1.LAST_NAME
FROM [SOOPS-LAWREPT].[LAWDATA].dbo.EMPLOYEE L1
 JOIN [SOOPS-LAWREPT].[LAWDATA].dbo.DEPTCODE L2 ON L1.Department = 
L2.Department
 JOIN [SOOPS-LAWREPT].[LAWDATA].dbo.JOBCODE L3 on L1.JOB_CODE = L3.JOB_CODE
 JOIN [SOOPS-LAWREPT].[LAWDATA].dbo.PRSYSTEM P1 ON L1.PROCESS_LEVEL = 
p1.PROCESS_LEVEL
WHERE  L1.EMP_STATUS='A1'


-- Select the Return Value
-------------------------------


IF (@AssignmentType = 'FirstName')
BEGIN
SET @ReturnValue = (SELECT TOP 1  LTRIM(RTRIM(t.MiddleName)) From @EIDTemp t 
where EID = @EID);
END

IF (@AssignmentType = 'MiddleName')
BEGIN
SET @ReturnValue = (SELECT TOP 1  LTRIM(RTRIM(t.MiddleName)) From @EIDTemp t 
where EID = @EID);
END

IF (@AssignmentType = 'LastName')
BEGIN
SET @ReturnValue = (SELECT TOP 1  LTRIM(RTRIM(t.LastName)) From @EIDTemp t 
where EID = @EID);
END

Answer 1

问题在于如何设置变量。当您使用SET时，如果没有返回任何行，它将更改为NULL。

您应该更改代码，以便它执行类似的操作。

SET @ReturnValue = 'Unknown'

IF (@AssignmentType = 'FirstName')
BEGIN
SELECT @ReturnValue = LTRIM(RTRIM(t.MiddleName)) From @EIDTemp t 
where EID = @EID
END

这会将初始值设置为“未知”。这将在您的所有IF语句之前，并将在整个集合中工作。如果没有返回行，则值将保持不变。我删除了TOP 1，因为它不需要。如果您有多行，它将从结果集的最后一行接收值。如果有很多行，你总是可以使用MAX或MIN。

Answer 2

@Perry，以下内容更像您所寻找的内容：

WITH employee_ids AS
(
    SELECT 
        emp.Employee AS eid
        ,P1.NAME As Section
        ,CASE 
            WHEN emp.DEPARTMENT IN (7010) THEN 
                'Legal Services Division' 
            WHEN emp.DEPARTMENT IN (7030,7040) THEN 
                'Fiscal Management Division'
            ELSE
                'Other'
            END AS Division
        ,CASE
            WHEN emp.DEPARTMENT IN (7130) THEN 
                'Administrative Services Bureau'
            ELSE 
                ','
            END As Bureau
        ,emp.FIRST_NAME
        ,emp.MIDDLE_NAME
        ,emp.LAST_NAME
        ,ROW_NUMBER() OVER (PARTITION BY emp.EMPLOYEE) AS eid_match

    FROM
        [SOOPS-LAWREPT].[LAWDATA].dbo.EMPLOYEE AS emp

    INNER JOIN 
        [SOOPS-LAWREPT].[LAWDATA].dbo.DEPTCODE AS depts 
        ON (emp.Department = depts.Department)

    INNER JOIN 
        [SOOPS-LAWREPT].[LAWDATA].dbo.JOBCODE AS jcs 
        ON (emp.JOB_CODE = jcs.JOB_CODE)

    INNER JOIN 
        [SOOPS-LAWREPT].[LAWDATA].dbo.PRSYSTEM AS prs 
        ON (emp.PROCESS_LEVEL = prs.PROCESS_LEVEL)

    WHERE
        emp.EMP_STATUS='A1'
)
,provisional_results AS
(
    SELECT
        CASE @AssignmentType
            WHEN 'FirstName' THEN
                employee_ids.FirstName
            WHEN 'MiddleName' THEN
                employee_ids.MiddleName
            WHEN 'LastName' THEN
                employee_ids.LastName
            ELSE
                NULL
            END AS provisional_return_value

    FROM 
        (VALUES (0)) AS default_values(default_value)

    LEFT JOIN 
        employee_ids
        ON (employee_ids.eid = @eid) 
        AND (eid_match = 1)
)
SELECT 
    @ReturnValue = ISNULL(LTRIM(RTRIM(provisional_return_value)), 'UNKNOWN') 
FROM 
    provisional_results

我还没有对我的桌面进行测试，因为我不在我的桌面上，所以请原谅任何小的语法错误，但它应该达到你所需要的。

Answer 3

运行insert / select后需要立即保存@@RowCount变量并返回变量。如果您不保存变量，另一个语句最终将清除行数...

示例：

--Variable to hold the rowcount DECLARE @Count int = 0 ... Insert Into @EIDTemp SELECT L1.Employee, P1.NAME As Section, ... WHERE L1.EMP_STATUS='A1' --Save the result SELECT @Count=@@RowCount ... --Use the saved result Case When @Count > 0 Then LTRIM(RTRIM(t.FirstName)) Else 'UNKNOWN' End

Answer 4

我的同事通过在开始时检查员工ID的值并使用此代码返回UNKNOWN来解决问题

> DECLARE @EID int = 0
DECLARE @AssignmentType varchar(max) = 'FirstName'

DECLARE @ReturnValue varchar(max) = 'UNKNOWN'
DECLARE @EIDTemp TABLE(EID varchar(6), Section varchar(max), Division 
varchar(max), Bureau varchar(max), FirstName varchar(max), MiddleName 
varchar(max), LastName varchar(max));

if @EID = 0
   goto done

-- Insert into a Temp Table
-------------------------------
Insert Into @EIDTemp
SELECT L1.Employee, P1.NAME As Section,
   CASE 
          WHEN L1.DEPARTMENT IN (7010) THEN 'Legal Services Division' 
          WHEN L1.DEPARTMENT IN (7030,7040) THEN 'Fiscal Management 
Division'
          Else 'Other'
   END AS Division,
   CASE
          WHEN L1.DEPARTMENT IN (7130) THEN 'Administrative Services Bureau'
          ELSE ','
   END As Bureau
   ,L1.FIRST_NAME
   ,L1.MIDDLE_NAME
   ,L1.LAST_NAME
FROM [SOOPS-LAWREPT].[LAWDATA].dbo.EMPLOYEE L1
   JOIN [SOOPS-LAWREPT].[LAWDATA].dbo.DEPTCODE L2 ON L1.Department = 
L2.Department
   JOIN [SOOPS-LAWREPT].[LAWDATA].dbo.JOBCODE L3 on L1.JOB_CODE = 
L3.JOB_CODE
   JOIN [SOOPS-LAWREPT].[LAWDATA].dbo.PRSYSTEM P1 ON L1.PROCESS_LEVEL = 
p1.PROCESS_LEVEL
WHERE  L1.EMP_STATUS='A1' AND l1.EMPLOYEE = @EID


-- Select the Return Value
-------------------------------


IF (@AssignmentType = 'FirstName')
BEGIN
   SET @ReturnValue = (SELECT TOP 1  LTRIM(RTRIM(t.FirstName)) From @EIDTemp 
t where EID = @EID);
END

IF (@AssignmentType = 'MiddleName')
BEGIN
   SET @ReturnValue = (SELECT TOP 1  LTRIM(RTRIM(t.MiddleName)) From 
@EIDTemp t where EID = @EID);
END

IF (@AssignmentType = 'LastName')
BEGIN
   SET @ReturnValue = (SELECT TOP 1  LTRIM(RTRIM(t.LastName)) From @EIDTemp 
t where EID = @EID);
END

done:

print @ReturnValue

我怎样才能检查0 ROWCOUNT

4 个答案: