DB2 SQL query to compare 2 schemas

问题

I have been unable to find a solution in my searching for this throughout the web, most responses recommend a tool, which leads me to believe this may be very difficult with an SQL query or something, but...

I have been told to write a query for our DB2 database, using Toad to interface, that will compare 2 schemas and provide a result if there are any differences. I know this capability exists in Toad, but for some reason our DBA does not want to use it. Purchasing additional software is not an option.

I have very limited SQL knowledge/experience, and this is one of my 'learning' tasks. I have not made much progress and am feeling very stuck. Can anyone offer me suggestions? The help is greatly appreciated!

回答1:

I assume by schemas you mean the schemas of a table, right? All that information is available through the views of the syscat schema. Look for instance at SYSCAT.TABLES and SYSCAT.COLUMNS, or see the documentation for more. You can query those views like any other view/table, so to compare if two tables contain the same columns, you can do something like:

  SELECT colname, colno, typeschema, typename FROM syscat.columns WHERE tabname = 'tab1' AND tabschema = 'schema'
  EXCEPT
  SELECT colname, colno, typeschema, typename FROM syscat.columns WHERE tabname = 'tab2' AND tabschema = 'schema'

This will, for instance, not return all the columns that are in tab1, but not in tab2.