SQL slow on DBase Table

Posted on 2000-02-14
Last Modified: 2013-11-24
I am running a SQL query on a DBase table with about 12 000 entries.  It is extremely slow.  The Query is as follows :

I know it is the order by clause that is slowing the query down but I must have it in.

I have one expression index on my Table:

VDate is a Date field And TLN is a number field(10, 0)

Can anybody please help me speed up this query?
Question by:Leon_b
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LVL 12

Expert Comment

ID: 2518091
I think you need to create separate indexes as the query may not use the expression index.


LVL 15

Expert Comment

ID: 2518230
Creating adequate indexes is an option... a very good one.

However, I must warn you that on file-based tables (like dBase, Paradox, etc), SQL is not necessarily faster than the TTable object. Neither dBase nor Paradox benefit from using SQL.

SQL is an advantage on database-based tables (like Access, MSSQL, Oracle, Iterbase, etc).


Expert Comment

ID: 2518577
Can't you be more specific than '*', I know it seriously increases speed if you literally specify the columns you need...

G'Luck !
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LVL 17

Expert Comment

ID: 2519380
 If you can perform all actions with the set in one loop from top to bottom, you can set UniDirectional property to true. Set it before preparing or executing the query.
  This will speed up your query but you lose backward functionality.
  I presume that you are using this query for printing some kind of report and you can modify your code to work unidirectional through the SQL set.

Regards, Geo

Author Comment

ID: 2521747
Thanks for all the suggestions, but nothing really speeds up the query enough.  I have a new question though regarding the same subject.

I took the ORDER BY out of the statement and ran it from SQL Explorer.  So in affect I ran a simple
SELECT * FROM TABLENAME query. In SQL explorer this query runs a lot faster than in my application even though the queries are exactly the same.

Why is this?
LVL 12

Expert Comment

ID: 2521774
Did it have indexes on the fields in the order by clause?

Author Comment

ID: 2521853

Accepted Solution

RLancaster earned 100 total points
ID: 2522073
specify the column names for a dramatic speed increase

another point to note is that TypedBinary fields seem to slow down queries dramatically ... try excluding these field types from your queries

this should help :)

Author Comment

ID: 2522084
It was the typed binary fields.  Removing these fields from the query Made a dramatic speed increase.  Thanx to everyone else trying to help.

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