How to get the list of non empty queries? - sql

Question

In MS Access I have 1 table that updates daily via external file and 50 queries (named 01_query, 02_query... 50_query), all with same columns and logic but with different filters. Some returns result, others are empty.
How can I get the list (using another query) with the names of NON empty queries?
I found the way to get a list of all query names with this code
SELECT MSysObjects.Name
FROM MsysObjects
WHERE (Left$([Name],1)<>"~") AND (MSysObjects.Type)=5
ORDER BY MSysObjects.Name
but I can't figure out how to filter out the "empty" queries.

Answer 1

If you absolutely must have an Access SQL solution to produce your list, consider something other than UNION of 50 data sources. Access does not allow you to UNION an unlimited number of data sources, but I don't recall what that limit is. And even if it allows you to UNION 50, I still wouldn't do it.
I tested this one in Access 2010 and it produces the result I think you're looking for. Since you've demonstrated you have read permission on MsysObjects it should work for you, too.
SELECT
sub.Name
FROM
(
SELECT
m.Name,
IIf(
m.Name ALike '[0-9][0-9][_]query' AND m.Type=5,
DCount('*', m.Name),
0
) AS non_empty_target_query
FROM MsysObjects AS m
) AS sub
WHERE sub.non_empty_target_query=True
ORDER BY sub.Name;
The IIf() expression is the key to this query. In human-like speak it says, if the object is a query and its name starts with 2 digits followed by an underscore followed by "query", return the count of rows from that query; otherwise just return zero.
Then the parent query filters away those rows where non_empty_target_query is zero (False), leaving only rows containing the names of your "non-empty" queries.

Answer 2

Assuming that all your queries follow the same format, you actually don't need to do anything with MSysObjects. You can just do a simple loop (in VBA):
Public Sub GetNonEmptyQueries()
Dim db As DAO.Database, qdf As DAO.QueryDef
Dim rs As DAO.Recordset
Dim queryName As String
Dim i As Integer
Set db = CurrentDb
For i = 1 To 50
queryName = format(i, "00") & "_query"
Set qdf = db.QueryDefs(format(i, "00") & "_query")
Set rs = qdf.OpenRecordset
If rs.recordCount > 0 Then
' do whatever you need to do with the query name here
Debug.Print qdf.Name
End If
Next i
End Sub
If you don't want to use VBA, it's possible to write a query that UNIONs the COUNT(*) of all your queries. Something like this:
SELECT "01_query" AS QueryName, Count(*) AS [Count] FROM 01_query HAVING COUNT(*) > 0
UNION
SELECT "02_query", COUNT(*) FROM 02_query HAVING count(*) > 0
...
UNION
SELECT "50_query", COUNT(*) FROM 50_query HAVING COUNT(*) > 0
Of course, you're going to have to add all the queries by hand, which is going to get rather tedious. I think the time you would spend hand-writing such a query might be better-spent reading up on VBA, so you can use the first option. :)