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In relational databases, the information schema (information_schema) is an ANSI-standard set of read-only views that provide information about all of the tables, views, columns, and procedures in a database. [1]
Oracle Database provides information about all of the tables, views, columns, and procedures in a database. This information about information is known as metadata. [1] It is stored in two locations: data dictionary tables (accessed via built-in views) and a metadata registry.
Some databases - like Oracle - provide a plan table for query tuning. This plan table will return the cost and time for executing a query. Oracle offers two optimization approaches: CBO or Cost Based Optimization; RBO or Rule Based Optimization; RBO is slowly being deprecated. For CBO to be used, all the tables referenced by the query must be ...
These can be defined either in plain SQL with CREATE TYPE but also in Java via SQL/JRT. SQL structured types allow single inheritance. Structured types are supported to varying degrees in Oracle Database, IBM Db2, PostgreSQL and Microsoft SQL Server, although the latter only allows structured types defined in CLR.
The database schema is the structure of a database described in a formal language supported typically by a relational database management system (RDBMS). The term " schema " refers to the organization of data as a blueprint of how the database is constructed (divided into database tables in the case of relational databases ).
In the context of SQL, data definition or data description language (DDL) is a syntax for creating and modifying database objects such as tables, indices, and users. DDL statements are similar to a computer programming language for defining data structures , especially database schemas .
Oracle SQL Developer supports Oracle products. In the past a variety of third-party plugins were supported which users were able to deploy to connect to non-Oracle databases. Oracle SQL Developer worked with IBM Db2, Microsoft Access, Microsoft SQL Server, MySQL, Sybase Adaptive Server, Amazon Redshift and Teradata databases. [4]
PL/SQL refers to a class as an "Abstract Data Type" (ADT) or "User Defined Type" (UDT), and defines it as an Oracle SQL data-type as opposed to a PL/SQL user-defined type, allowing its use in both the Oracle SQL Engine and the Oracle PL/SQL engine. The constructor and methods of an Abstract Data Type are written in PL/SQL.