PHP SQL - primary keys and an index

Author

primary keys and an index

davidklonski

2004-08-18, 3:57 pm

Hello MySQL gurus

Assuming I create the following table:

CREATE TABLE table (
ID INT UNSIGNED NOT NULL AUTO_INCREMENT,
Column1 INT UNSIGNED NOT NULL,
Column2 VARCHAR(255) NOT NULL,
PRIMARY KEY (ID)
) ENGINE=MYISAM DEFAULT CHARSET=latin1;

Now ID is the primary key of the table which means it has a unique
index on it (right?)

will adding the following have any additional effect?
CREATE index_name ON table(ID);

Or is such an index automatically created for all the primary keys in
a table?

Also, putting storage issues aside, what would be the di

vantages to
creating an index for every column that I use in a join, (in order to
speed things up)?

thanks for the help

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Barand

2004-08-18, 3:57 pm

Primary key (ID) is already a unique index.

As for di

vantages, can't see any besides storage.

Also, if you regularly have queries which ... ORDER BY column2,
column1 ... then it may be worth considering an index on those
fields.

Barand

http://members.aol.com/barryaandrew...agridguide.html easy
data tables - and more

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