[cfaussie] Re: Somewhat OT : SQL Left Join

[Brett Payne-Rhodes]

Hi Andrew,

Answers below...

Andrew Dickinson wrote:
I'm taking my first cautious steps into coding with Left/Right Joins.

If a record is in one table but not another, what value is expressed ? Is
it Null ?
Yes.

I'm looking for a way to capture "in onr table but not another" as a value
to increment an array-variable.
The approach I'm currently using has one "driver" query with three queries
nested inside it, and it is of course horrendously slow (about 180
seconds).
Using an outer join may not improve things if some underlying issue is 
causing the time taken to execute the query. Does your DBMS support the 
"analyse" function? Can you add indexes to help the execution time? You 
could also try posting your query here...

hth

Brett
B)
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Brett Payne-Rhodes
Eaglehawk Computing
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