Database Reference
In-Depth Information
The Oracle Server supports a very comprehensive system catalog. There are system
tables for all the database object types supported. These include (but are not confined to):
•
Databases
•
Tablespaces
•
Datafiles
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(Database) Tables
•
Sequences
•
Columns of tables
•
Constraints (Cons-tables and Cons-columns)
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Synonyms
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Logical views
•
Indexes
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Privileges (Role_privs and Table_privs)
•
Table_Comments
•
Column_Comments
These tables are typically accessed indirectly via logical views prefixed by 'DBA' ,
'User' or 'All' (e.g. we have DBA_tables, User_tables and All_tables).
16.2.2 Oracle PL/SQL and SQL *Plus
Oracle has its own host language, PL/SQL. This high level language (very Pascal-like) is
what is typically used to develop an application (although Java is supported).
PL/SQL was specifically developed for Oracle applications and is portable on Oracle
Servers. It exhibits all the main features of a classical HLL, but avoids ambiguities (for
instance about the If-Statement). PL/SQL is a limited HLL; it focuses solely on database
application development. It has limited treatment of arrays and pointers.
Oracle provides a standard SQL Editor through SQL *Plus. SQL *Plus is a basic line
editor that allows you to enter and SQL statements. You were introduced to basic SQL
*Plus commands in section 11.1. Due to its limitations, many Oracle users tend to use
other text editors to specify SQL instructions and integrate them into SQL *Plus.
This process is seamless and is handled quite well by SQL *Plus.
