The schemas table is used during component installation to handle installing bulk SQL queries and progressively playing through them.
|extensionid||int(11)||NOT NULL||PRI||Unique extension identifier, see #__extensions|
|schemaid||varchar(20)||NOT NULL||PRI||Schema Unique Identifier|
This table is a simple store of schema version numbers to be used with component upgrades in 1.6 that have schema upgrades. This is handled automatically by the system.