At 17:10 9/11/00 +0100, Zeugswetter Andreas SB wrote:
>
>> 3. Schemas are what we call databases. They contain tables, views wtc.
>
>Let us not start this all over again. Our database would correspond to a
catalog
>if we put schemas below our database hierarchy.
>
>The standard requires, that you see all schemas within one catalog in
>one user session. We do not see tables in another database,
>thus our database is not equivalent to ANSI schemas.
We could run around in circles here: you can't define tables in a catalog,
so our database must be a schema...so it seems that our database is part
catalog, part schema. The important question is how can we most efficiently
implement schemas & catalogs, and I assume that implementing multiple
database connections in one backend process would require a lot more work
than putting a schema layer into our current 'databases'.
>The standard also requires, that you can qualify a tablename with a schema,
>like: "myschema".tabname. This will be the most difficult thing for us.
The way Dec/RDB handled this transition was to have a default schema. ie.
you could 'attach' to a schema as the default schema (which happened by
default, no pun intended). Subsequent table references that were not
qualified by a schema name were assumed to be from this default schema. You
could subsequently attach to another schema and either (a) specify a schema
alias, or (b) override the default schema.
I think you can also use the schema name to qualify tables without an
explict attach (assuming you are in the catalog).
Perhaps '\connect catalog.schema' would open the catalog and make 'schema'
the default schema.
This way, client programs and users suffer the minimum confusion.
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