To get a list of all columns within a database, you can use the ANSI compliant INFORMATION_SCHEMA.COLUMNS system view.
SELECT * FROM INFORMATION_SCHEMA.COLUMNS
In order to get all the columns in all the databases however, you need to loop through the databases. To do this, you can use the undocumented sp_MSForEachDB procedure that Microsoft ships.
sp_MSForEachDB @command1='USE ?; SELECT Table_Catalog ,Table_Schema ,Table_Name ,Column_Name ,Data_Type ,Character_Maximum_Length FROM INFORMATION_SCHEMA.COLUMNS'
