How To SQL Join Tables, Selecting The Largest Value In Access-VBA Function?

I currently have the following Access VBA function, which operates as explained in a previous question (very useful for understanding this question): Private Function MapFields(tab

Solution 1:

Encode value, decode max this way in SQL.

Currently you are building SQL command as (i replaced table name variables with arbitrary values, temp and tableName )

SELECT tbl_grp_by.*, [tableName].*  
INTO newTableName 
FROM (
    SELECT Max([temp].[Field1]) as [Field1], 
        Max([temp].[Field2]) as [Field2],  
        Max([temp].[Field3]) as [maxField3], 
        [temp].[Field4] as [Field4]  
    FROM [temp]
    INNER JOIN [tableName ]
       ON [temp].[commonField] = [tableName].[commonField] 
    GROUP BY [temp].[commonField]
 ) as tbl_grp_by  
INNER JOIN [tableName]
  ON [tableName].[commonField] = tbl_grp_by.[commonField]

Build it as

SELECT tbl_grp_by.[Field1],tbl_grp_by.[Field2],
    Switch( 
        tbl_grp_by.[maxfield3] = 0, '0',
        tbl_grp_by.[maxfield3] = 1, '>1 million',
        tbl_grp_by.[maxfield3] = 2 '0001-0010' 
    ) as [Field3],   
    tbl_grp_by.[Field4],
[tableName].*  
INTO newTableName 
FROM (
    SELECT Max([temp].[Field1]) as [Field1], 
        Max([temp].[Field2]) as [Field2],  
        Max(Switch(  
            [temp].[field3] = '0' , 0,
            [temp].[field3] = '>1 million' , 1,
            [temp].[field3] = '0001-0010', 2  
         ))as [maxField3], 
        [temp].[Field4] as [Field4]  
    FROM [temp]
    INNER JOIN [tableName ]
       ON [temp].[commonField] = [tableName].[commonField] 
    GROUP BY [temp].[commonField]
 ) as tbl_grp_by  
INNER JOIN [tableName]
  ON [tableName].[commonField] = tbl_grp_by.[commonField]   

So [field3] is encoded under max() in the inner query and that max is decoded in outer query.

Solution 2:

I would consider creating a reference table with value field as it easier to maintain specially when the values change overtime.

CREATE TABLE tblReference (field_txt text, val Integer);

Get the field_txt with highest value and unique field then left join(inner join) to your current dataset.

qry_field3_max = "SELECT [Field3],[commonField] FROM tblReference INNER JOIN (SELECT [commonField], MAX(val) as val FROM tblReference INNER JOIN tblNameTemp on tblReference.[field_txt]=tblNameTemp.[Field3] Group By [commonField]) as tbl_max_fields on tblReference.val=tbl_max_fields.val"