Oracle metadata
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The ORACLE application server and Oracle relational database keep metadata in two areas: data dictionary tables (accessed by built-in functions) and a metadata registry.
The global built-in functions 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 functions 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 "DBA_" metadata functions require DBA privileges.
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[edit ] Example 1: finding tables
Find all Tables that have PATTERN in the table name and are not backup or temporary tables
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
Count the total number of rows in all tables containing a column name that matches PATTERN ==
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;
[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, EMM is available only through Oracle consulting services.
[edit ] See also
[edit ] External links
