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MySQL INDEXes (indices?)

PHP @ December 30, 1969   Views:0

a couple of INDEX related questions. (i tried posting on the MySQL.com forum but got no response, feel free to point me to a good MySQL forum if there is one).

i've been looking at some of my old databases with a view to optimising them as i'm totally self-taught and never realised loads of stuff like indexing when i created the databases! i'm using MySQL 3.23.58, all tables using MyISAM.

on one of my tables (orders) i have built an index on the customer ID field but when i view it in phpMyAdmin this index has the same cardinality as the PRIMARY index (i.e. order number). now i know for sure that some customers have ordered more than once, so shouldn't the cardinality of the customer INDEX be lower than the PRIMARY INDEX? the customer ID field is type MEDIUMINT(8).

on another database, in another table, i have 4 text columns for varying degrees of scientific calculations (species, genus etc). i have built a FULLTEXT index across the 4 columns as i want non-scientific people (who don't understand the difference between genus, species etc) to be able to query the database. now i don't seem to be able to add any other INDEXes on this table. i want to index the genus column by it's first letter so i can browse the table by letter. this works fine without the FULLTEXT INDEX but not with. is this right that a FULLTEXT INDEX can be the only INDEX (other than the PRIMARY) on a table.



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