assertion, drop schema, list tables

I am having trouble with dropping schema and enforcing constraints. I am working on my DB class project. Some of our requirements need to check simple integrities. So, I want to create assertion to enforce the integrities. Yet, Oracle 7. complains the assertion statment, such as:

	create assertion <name>
	check (not exist(
			select ...
			from   ...
			where  ...));

It seems I can not create assertion. I wuold like to know if there is equivalent command that I can enforce the constraints.

Anothe problem I have is to drop a schema. I created schemas without knowing how to drop it. Then, after creating several small tables, I got an error , " failed to allocate extent of size 25 in tablespace 'CS440_TS'". I am wondering if the schemas are the reasons why I can not create any more tables in DB. Anyway, I don't use the schemas. I want to drop them. But, I don't know how.

The last one is to list all the tables in DB. Although I created the tables, I don't know how to list the tables I created.

If there is anyone who can answer any of the questions( problems ) above, please let me know.

e-mail:
june_at_sage.cc.purdue.edu

Thanks! Received on Mon Apr 04 1994 - 07:44:57 CEST