Oracle metadata

From Wikipedia, the free encyclopedia

The introduction to this article provides insufficient context for those unfamiliar with the subject. Please help improve the article with a good introductory style. (October 2009)

The ORACLE application server and Oracle relational database keep metadata in two areas: data dictionary tables (accessed via built-in views) and a metadata registry. The total number of these views depends on the Oracle version, but is in a 1000 range.

The few main built-in views accessing Oracle RDBMS data dictionary tables are:

• ALL_TABLES - list of all tables in the current database that are accessible to the current user
• ALL_TAB_COLUMNS - list of all columns in the database that are accessible to the current user
• ALL_ARGUMENTS - lists the arguments of functions and procedures that are accessible to the current user
• ALL_ERRORS - lists descriptions of errors on all stored objects (views, procedures, functions, packages, and package bodies) that are accessible to the current user
• ALL_OBJECT_SIZE - included for backward compatibility with Oracle version 5
• ALL_PROCEDURES - (from Oracle 9 onwards) lists all functions and procedures (along with associated properties) that are accessible to the current user
• ALL_SOURCE - describes the text (i.e. PL/SQL) source of the stored objects accessible to the current user

In addition there are equivalent views prefixed "USER_" which show only the objects owned by the current user (i.e. a more restricted view of metadata) and prefixed "DBA_" which show all objects in the database (i.e. an unrestricted global view of metadata for the database instance). Naturally the access to "DBA_" metadata views requires specific privileges.

Contents 1 Example 1: finding tables 2 Example 2: finding columns 3 Example 3: counting rows of columns 4 Use of underscore in table and column names 5 Oracle Metadata Registry 6 See also 7 External links

[edit] Example 1: finding tables

Find all Tables that have PATTERN in the table name

  SELECT
     TABLE_NAME
  FROM
     ALL_TABLES
  WHERE
     TABLE_NAME LIKE '%PATTERN%'
  ORDER
     BY TABLE_NAME;

---

[edit] Example 2: finding columns

Find all tables that have at least one column that matches a specific PATTERN in the column name

  SELECT
     TABLE_NAME,
     COLUMN_NAME
  FROM
     ALL_TAB_COLUMNS
  WHERE
     COLUMN_NAME LIKE '%PATTERN%';

[edit] Example 3: counting rows of columns

Estimate a total number of rows in all tables containing a column name that matches PATTERN (this is SQL*Plus specific scriot)

  COLUMN DUMMY NOPRINT
  COMPUTE SUM OF NUM_ROWS ON DUMMY
  BREAK ON DUMMY
  SELECT
     NULL DUMMY,
     T.TABLE_NAME,
     C.COLUMN_NAME,
     T.NUM_ROWS
  FROM
     ALL_TABLES T,
     ALL_TAB_COLUMNS C
  WHERE
     T.TABLE_NAME = C.TABLE_NAME
     AND C.COLUMN_NAME LIKE '%PATTERN%'
  ORDER BY T.TABLE_NAME;

Note that NUM_ROWS records the number of rows which were in a table when (and if) it was last analyzed. This will most likely deviate from the actual number of rows currently in the table.

[edit] Use of underscore in table and column names

The underscore is a special SQL pattern match to a single character and should be escaped if you are in fact looking for an underscore character in the LIKE clause of a query.

Just add the following after a LIKE statement:

  ESCAPE '_'

And then each literal underscore should be a double underscore: __

Example

  LIKE '%__G' ESCAPE '_'

[edit] Oracle Metadata Registry

The Oracle product Oracle Enterprise Metadata Manager (EMM) is an ISO/IEC 11179 compatible metadata registry. It stores administered metadata in a consistent format that can be used for metadata publishing. As of January 2006^[update], EMM is available only through Oracle consulting services.

[edit] See also

• metadata

[edit] External links

• article on Oracle Metadata

This computer science article is a stub. You can help Wikipedia by expanding it. v • d • e