How does one use the "create database" statement for Oracle express 11g?

Question

According to one of my posts (below) it seems that there is no such thing as a database in Oracle. What we call database in MySQL and MS-SQL is called schema in Oracle. If that is the case, then why do the oracle docs mention the create database statement ? For the record, I am using Oracle 11g and oracle SQL Developer GUI tool.

Post- How to create a small and simple database using Oracle 11 g and SQL Developer?

The create database statement from oracle docs is given below. If there is no database concept, then how did this command come into the picture ?

CREATE DATABASE
CREATE DATABASE [ database ]
{ USER SYS IDENTIFIED BY password
| USER SYSTEM IDENTIFIED BY password
| CONTROLFILE REUSE
| MAXDATAFILES integer
| MAXINSTANCES integer
| CHARACTER SET charset
| NATIONAL CHARACTER SET charset
| SET DEFAULT
{ BIGFILE | SMALLFILE } TABLESPACE
| database_logging_clauses
| tablespace_clauses
| set_time_zone_clause
}... ;

Justin Cave Justin Cave · Accepted Answer · 2012-08-08T00:02:47

There is concept of a "database" in Oracle. What the term "database" means in Oracle terms is different than what the term means in MySQL or SQL Server.

Since you are using the express edition, Oracle automatically runs the CREATE DATABASE statement as part of the installation process. You can only have 1 express edition database on a single machine. If you are installing a different edition, you can choose whether to have the installer create a database as part of the installation process or whether to do that manually via the CREATE DATABASE statement later. If you are just learning Oracle, you're much better off letting Oracle create the database for you at installation time-- you can only create the database via command-line tools (not SQL Developer) and it is rare that someone just starting out would need to tweak the database settings in a way that the installer didn't prmopt you for.

In Oracle, a "database" is a set of data files that includes the data files for the SYS and SYSTEM schemas which contain all the Oracle data dictionary tables, the data files for the TEMP tablespace where sorts and other temporary operations occur, and the data files for whatever schemas you want to create. In SQL Server and other RDBMSs, these would be separate "databases". In SQL Server, you have a master database, a tempdb database, additional database for different products (i.e. msdb for the SQL Server Agent), and then additional user-defined databases. In Oracle, these would all be separate schemas in a larger container that Oracle refers to as a "database".

Occasionally, a DBA will want to run multiple Oracle databases on the same server-- most commonly when there are different packaged applications that have different requirements about database versions or parameters. If you want to run application A that requires an 11.2 database and application B that doesn't support 11.2 yet, you would need to have two different databases on the server. The DBA could create a separate database and a separate instance but that doubles the memory requirements, doubles the number of background processes required to run the database, and generally makes things less scalable. It's necessary if you really want to run different versions of the database simultaneously but it's not ideal.

How does one use the "create database" statement for Oracle express 11g?

2 Answers