628 CHAPTER 28 FROM DATABASES (Geocities web hosting) TO DATATYPES
628 CHAPTER 28 FROM DATABASES TO DATATYPES Altering Schemas You can change the name of a schema by using the ALTERSCHEMA command: ALTER SCHEMA rob RENAME TO robert; Dropping Schemas Dropping a schema is done through the DROPSCHEMA command. By default, you cannot drop a schema that contains any objects. You can control this by using the CASCADE or RESTRICT keywords: DROP SCHEMA robert CASCADE; The Schema Search Path Once you begin adding schemas into your database, you will quickly begin to realize that working with multiple schemas can be a pain when you have to reference every object with a fully qualified schemaname.tablename notation. To get around this problem, PostgreSQL supports a schema search path setting akin to the search paths used for executables and libraries in most operating systems. In order for the operating system to find an executable or library, you first have to tell it where to look by giving it a list of directories that could contain the item of interest. Then, you have to place the item into one of these directories. The same applies to the PostgreSQL search path. When you reference a table with an unqualified name, PostgreSQL searches through the schemas listed in the search path until it finds a matching table. You can view the current search path with the following command: rob=# show search_path; Running this command will show the search path: search_path $user,public (1 row) The default search path is equivalent to a schema with the same name as the current user, and then the public schema, which is the default schema created for all databases. You can change the search path by issuing a set command, like so: set search_path=”$user”,public,mynewschema; This would add the schema mynewschemainto the search path, and allow any tables, views, or other system objects to be referenced unqualified. Consider the following command that lists all customer tables in the search path: company=# dt *.customer As you can see, the new schema is included in the results:
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