A table is the basic building block for storing data in the database. Conceptually, a table is a file that is created and maintained within the data files assigned to the database.
When a user creates a table, he or she specifies parameters such as the table name, the column names, their data types, and their lengths. The tablespace is also usually specified in the CREATE statement to ensure that the table is created in the proper tablespace. If a tablespace name is not specified, the table will be created in the user’s default tablespace. An initial amount of space is specified for the table’s data using the INITIAL parameter of the STORAGE clause in the CREATE TABLE statement. When that amount of space is filled, more space will be allocated based on the value set by the NEXT parameter in the STORAGE clause. If no STORAGE clause is present in the CREATE TABLE statement, the default storage values of the tablespace in which the table has been created will be used. The kernel handles this allocation, and the space comes from the datafiles assigned to the tablespace in which the table was created.
Suppose the database has a data01
tablespace and there are three datafiles named
persdata03.dbf associated with the data01
mary creates a table named
“employee” and specifies the data01 tablespace. A command
such as the following might be used while
is logged into SQL*Plus: ...