Different databases use different industry classifications. Here is a (non-exhaustive) list of classifications:
SIC -Standard Industrial Classification
ICB -Industry Classification Benchmark
Classification of Dow Jones Indexes and FTSE. Used in Thomson One
The North American Industry Classification System
The standard used by Federal statistical agencies in classifying business establishments for the purpose of collecting, analyzing, and publishing statistical data related to the U.S.business economy.
(choose GICS Maps)
Global Industry Classification Standard
Developed by Standard & Poor’s and MSCI Barra, GICS consists of 10 sectors, 24 industry groups, 68 industries and 154 sub-industries.
Thomson Reuters Business Classification system.
TRBC consists of four levels of hierarchical structure. Each company is allocated an Industry, which falls under an Industry group, then Business Sector, which is then part of an overall Economic Sector. There are 10 Economic Sectors, 25 Business Sectors, 52 Industry Groups and 124 Industries.
USED IN DATASTREAM!
Orbis uses the NACE industry classifications made by the European Commission. They also have a convertor from other industry classifications to this NACE.