Schema definitionsSchema definitions mk Sat, 03/27/2010 - 22:50
A SCHEMA is a container for tables, views, indices, triggers, functions and procedures. Schema access and modification is strictly controlled using the user role and authorisation scheme.
Every SCHEMA belongs to a database. One reason for organizing the logically separated data in schemas rather than databases is that in this way there will still be just one MonetDB process running.
The DEFAULT CHARACTER SET and PATH options are here for compatibility reasons with the the SQL standard, however they are not yet implemented. The default character set is UTF-8.
ident | [ ident ] AUTHORIZATION ident
The AUTHORIZATION option allows specifying the name of the user or the role that will own the schema. If omitted, the user who has executed the query will be the owner. The owner of the schema is allowed to create, alter and drop tables. With the AUTHORIZATION option, an explicit name for the schema is optional. If omitted, the schema automatically gets the name of the authorised user/role as its name.
Notes on schema creation:
- The ownership of a schema can be assigned to only one user/role, and it can not be modified after its creation. Therefore, to share the ownership of a schema, one must assign the ownership of a schema to a role at the creation of the schema. Subsequently, the role can be granted to multiple users to own the schema.
- Only the 'monetdb' user and the 'sysadmin' role can create a new schema. Therefore, to allow other users other to create schema, the 'monetdb' user should assign the 'sysadmin' role to the intended users.
grant | revoke | create_statement | drop_statement | alter_statement
| DROP SCHEMA qname drop_action
RESTRICT | CASCADE
The drop_action option is supported for compatibility with the SQL standard, however it is not implemented yet. Currently it runs with the CASCADE option, meaning that once a schema is dropped every object inside the schema is dropped as well, such as tables and functions. However objects that are dependent on the schema, such as users will not automatically be dropped and will stop the schema from being dropped as well. One can either ALTER the user and give it a different default schema, or to simply drop the user if it is no longer needed.
| SET SCHEMA ident
When opening the database, by default the “sys” schema is set. Another automatically created schema is “tmp”, used for temporally local tables. It is not possible for a user to access the “tmp” schema of another user.
One can create a new schema using the CREATE command and change to it, by using the SET command. When creating a table without specifying the schema, the table will be created in the schema that is currently in usage. In order to create a table in a different schema, use the schema name as a prefix.