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Editorial Team
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Asked: 2026-06-16T09:02:59+00:00

i am trying to make a query but it is not right. what i

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i am trying to make a query but it is not right.

what i want to do is to apply join in case

my query is

SELECT LEFT(Student_First_Name,LEN(Student_First_Name)-LEN(Name_Lookup_Table.Dirty_Name)),Name_Lookup_Table.Dirty_Name, Name_Lookup_Table.Standard_Name

case
when Transformed_All_Student.Student_First_Name like '% '+Name_Lookup_Table.Dirty_Name
then
from Transformed_All_Student left join Name_Lookup_Table 
on Transformed_All_Student.Student_First_Name like '% '+Name_Lookup_Table.Dirty_Name

when Transformed_All_Student.Student_First_Name like '% '+Name_Lookup_Table.Dirty_Name+'%'
then from Transformed_All_Student left join Name_Lookup_Table on Transformed_All_Student.Student_First_Name like '% '+Name_Lookup_Table.Dirty_Name+'%'

when Transformed_All_Student.Student_First_Name like Name_Lookup_Table.Dirty_Name+'% '
then from Transformed_All_Student left join Name_Lookup_Table on Transformed_All_Student.Student_First_Name like Name_Lookup_Table.Dirty_Name+'% '

can anyone help??

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1 Answer

  1. Editorial Team

    I do not think you can put FROM in case when. one possible solution is using UNION. You probably can optimize this:

        SELECT LEFT(Student_First_Name
        , LEN(Student_First_Name)-LEN(nlt.Dirty_Name))
        , nlt.Dirty_Name
        , nlt.Standard_Name

    FROM Transformed_All_Student tas
            LEFT JOIN Name_Lookup_Table nlt
                        ON tas.Student_First_Name like '% '+nlt.Dirty_Name
    WHERE tas.Student_First_Name like '% '+nlt.Dirty_Name

    UNION

    SELECT LEFT(Student_First_Name
        , LEN(Student_First_Name)-LEN(nlt.Dirty_Name))
        , nlt.Dirty_Name
        , nlt.Standard_Name

    FROM Transformed_All_Student tas 
            LEFT JOIN Name_Lookup_Table nlt 
                ON tas.Student_First_Name like '% '+nlt.Dirty_Name+'%'

    WHERE tas.Student_First_Name like '% '+nlt.Dirty_Name+'%'

    UNION

    SELECT LEFT(Student_First_Name
        , LEN(Student_First_Name)-LEN(nlt.Dirty_Name))
        , nlt.Dirty_Name
        , nlt.Standard_Name
    FROM Transformed_All_Student tas 
            LEFT JOIN Name_Lookup_Table nlt 
                    ON tas.Student_First_Name like nlt.Dirty_Name+'% '

    WHERE tas.Student_First_Name like nlt.Dirty_Name+'% '
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