Conference bump::msaccess

    
    	A "problem" realted to the title of the base note but not the
    	content:
    
    	I somehow ended up with a query that had 4 tables, and output
    	fields from all 4 tables, but no indicated relationships between
    	the tables [IE, there was no joining of fields specified].  So I
    	ran it, and it went on and on for a long time before I finally
    	stopped it.
    
    	What was Access trying to do?  I figured it'd give me the output
    	from all 4 tables in succession with no matching records from
    	the other tables:
    
    	Field Field Field Field Field Field Field Field
            1     1
            1     1
                        1     1
                        1     1
                                    1     1
                                    1     1
                                                1     1
                                                1     1

    
	So, what WAS it trying to do?
    

Apparently this will produce a 'Cartesian product', which Help defines as:


"Cartesian product

The result of joining two relational tables, producing all possible ordered 
combinations of rows from the first table with all rows from the second 
table. 
Generally, a cartesian product results from executing a SQL SELECT statement 
referencing two or more tables in the FROM clause and not including a WHERE 
or JOIN clause that indicates how the tables are to be joined."

That means that if the four tables have N1, N2, N3 and N4 records in them 
respectively, the output will be a recordset with N1 * N2 * N3 * N4 records.

This is standard relational database behaviour.

Brian.

    
    	Thanks.  I tried looking through the Access V2 book but couldn't
    	find anything and didn't know how to look it up.
    
    	And A*B*C*D would have been quite large, since A and B alone are
    	23K records each.