1) Table _catalog menat to hold the database name, but in most cases postgis just leaves that blank since there is a geometry_columns table per database. I'm not quite sure if the specs require that be filled in though. In theory it should since the standard ANSI SQL information_schema tables require it filled in. 2) Well as you may have noticed - Postgis doesn't follow the MM Part 3 spec yet as for as these meta tables are concerned e.g. they don't start with ST_ yet and geometry_columns is a physical table. I haven't taken that close a look at the specs to see if they really require SRS_Name be the primary key. Are you sure that is the case. Most systems I know of based on my limited understanding key off of the SRS_SRID. Having the SRS_NAME be unique however doesn't seem like a bad idea since it would prevent equivalent spatial reference systems from having 2 different identities. Hope that helps, Regina
________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of zhangmb Sent: Wednesday, July 09, 2008 5:44 AM To: postgis-users@postgis.refractions.net Subject: [postgis-users] questions about geometry_columns base table! Hello,I have some questions about SQL/MM part 3:spatial. 1. In the definition of st_geometry_columns base table, what is the meaning of the TABLE_CATALOG and what it should store exactly? what is the meaning of the unqualified schema name and the qualified identifier? 2. In the definition of st_spatial_reference_systems base table, why using SRS_NAME as primary key as opposed to using SRS_SRID? Thanks a lot! --zhangmb ----------------------------------------- The substance of this message, including any attachments, may be confidential, legally privileged and/or exempt from disclosure pursuant to Massachusetts law. It is intended solely for the addressee. If you received this in error, please contact the sender and delete the material from any computer.
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