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Where and join
Message
From
30/12/1999 18:33:55
 
 
To
30/12/1999 18:30:19
General information
Forum:
Visual FoxPro
Category:
Databases,Tables, Views, Indexing and SQL syntax
Title:
Miscellaneous
Thread ID:
00310742
Message ID:
00310748
Views:
26
Dear all,

Please confirm somebody the following behaviour:

select anything from a inner join b on a.field=b.field where into anything

I faced, that VFP creates and intermediate cursor where it packs into all records, that meets the join condition, and THEN will create the final result, that contains only those records that meet where clause.

So, now I place select criteria into join condition, too. Like

Instead of:

select anything from a inner join b on a.field=b.field where a.field>0 into anything

I use:

select anything from a inner join b on a.field=b.field and a.field>0 where a.field>0 into anything

Of course, it is not a problem when the number of filtered records are relativly little.

But a two big (?) 10M, inner joined table produced me an INSUFFICIENT DISK SPACE error message. (It produced a +150M intermediate cursor and 25 sec run time)

Hmmm...

bb

P.S. Sorry, HTML tags drive me up to the wall
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