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Index Question using Access 2000
- Thread starter frenchy62
- Start date
Hi
Indexes have several uses
to quickly locate rows a table without reading all rows, for example say we have a table of details about people, and one of the columns is Date of birth. If we want to locate all people born on a given day we need to read through everyrow in the table checking the DOB, but if we have an index on that row we simply look in the index and retrieve only the relevant rows
To enforce uniqueness, but specifying that an index cannot have duplicates we can enforce uniqueness
The question of multiple column indexes does not impact on their use(s), just consider a table of Purchase Orders and Purchase Purchase order Items, we may index the Purchase Order Table on Purchase Order Number (Uniquely), but each PO can have n items, so we cannot get a unique index on the items table just on Purchase Order Number. But if we make a single index on the two columns Purchase Order Number, Purchase Order Item, then we have a unique index
Regards
Ken Reay
Freelance Solutions Developer
Boldon Information Systems Ltd
Website needs upgrading, but for now - UK
Indexes have several uses
to quickly locate rows a table without reading all rows, for example say we have a table of details about people, and one of the columns is Date of birth. If we want to locate all people born on a given day we need to read through everyrow in the table checking the DOB, but if we have an index on that row we simply look in the index and retrieve only the relevant rows
To enforce uniqueness, but specifying that an index cannot have duplicates we can enforce uniqueness
The question of multiple column indexes does not impact on their use(s), just consider a table of Purchase Orders and Purchase Purchase order Items, we may index the Purchase Order Table on Purchase Order Number (Uniquely), but each PO can have n items, so we cannot get a unique index on the items table just on Purchase Order Number. But if we make a single index on the two columns Purchase Order Number, Purchase Order Item, then we have a unique index
Regards
Ken Reay
Freelance Solutions Developer
Boldon Information Systems Ltd
Website needs upgrading, but for now - UK
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