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update items set requiredskillrank = 0

This will only require your players to learn a profession to use or enchant items.

To remove Faction requirements
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Update items set requiredfaction = 0

Maintenance Queries

To delete accounts no longer used (select your won date)
Change -wow- to the name of your database

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DELETE FROM `wow`.`accounts` WHERE `lastlogin` < '2009-01-15 00:00:00';

List of all the mobs without model.

SELECT `entry` FROM `creature_proto` WHERE `entry` NOT IN (SELECT `entry` FROM `creature_spawns`);

List of items that have bigger sell price then buy price.
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select * from `items` where `BuyPrice`<`SellPrice`;