Level Extreme platform
Subscription
Corporate profile
Products & Services
Support
Legal
Français
Problem
Message
 
 
General information
Forum:
Visual FoxPro
Category:
Databases,Tables, Views, Indexing and SQL syntax
Title:
Miscellaneous
Thread ID:
00396098
Message ID:
00396157
Views:
10
>>By the way, I have heard that SQL's work slower when tables are ordered. Is that true?
>>
>
>Yes, where reference is made to an existing open table by alias, and the work area has an index in effect, since if there's an index in effect on the alias and the table needs to be traversed record by record, it'll have to be traversed in the index order in effect in the work area referenced. This means that each time you move from one record to the next, the index is consulted to determine which record gets visited next. If no index is active (SET ORDER TO 0) then the overhead of record traversal by lookup in the index is removed.

Ed,
How is this possible? A SQL Select opens the the tables again in a new work area in order to have free reign to determine the best index to use, etc. How does the original order affect it?

I can see where commands like LOCATE or SCAN would be hurt.
Larry Miller
MCSD
LWMiller3@verizon.net

Accumulate learning by study, understand what you learn by questioning. -- Mingjiao
Previous
Next
Reply
Map
View

Click here to load this message in the networking platform