The following query (taken from real-life application):

EXEC sp_tables NULL, NULL, NULL, '''''''SYSTEM TABLE'''',''''TABLE'''',''''VIEW'''''''

returns correct results in MSSQL, but returns empty results in Babelfish.

This query is likely originates from mssql-jdbc implementation of JDBC getTables method. Empty result from sp_tables call does not allow table introspection to work.

Note, that @table_type parameter to sp_tables in this case is quote-escaped twice by the client app. Normal single quote-escaping works correctly in Babelfish:

EXEC sp_tables NULL, NULL, NULL, '''SYSTEM TABLE'',''VIEW'',''TABLE'''