Oracle metadata

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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.

Other relational database management systems support an ANSI-standard equivalent called information schema.

The total number of these views depends on the Oracle version, but is in a 1000 range.

The main built-in views accessing Oracle RDBMS data dictionary tables are few, and are as follows:

• ALL_OBJECTS – list of all objects in the current database that are accessible to the current user;
• ALL_TABLES – list of all tables in the current database that are accessible to the current user;
• ALL_VIEWS – list of all views 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;
• ALL_TRIGGERS – list all the triggers 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.

Find all Tables that have PATTERN in the table name

  SELECT Owner AS Schema_Name, Table_Name   FROM   All_Tables   WHERE  Table_Name LIKE '%PATTERN%'   ORDER  BY Owner, Table_Name; 

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

  SELECT Owner AS Schema_Name, Table_Name, Column_Name   FROM   All_Tab_Columns   WHERE  Column_Name LIKE '%PATTERN%'   ORDER  BY 1,2,3; 

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

  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%'    AND T.OWNER = C.OWNER   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.

Find view columns

SELECT TABLE_NAME,     column_name,     decode(c.DATA_TYPE,        'VARCHAR2',        c.DATA_TYPE || '(' || c.DATA_LENGTH || ')',        'NUMBER',        DECODE(c.data_precision,             NULL,             c.DATA_TYPE,             0,                  c.DATA_TYPE,             c.DATA_TYPE || '(' || c.data_precision || DECODE(c.data_scale,                                     NULL,                                     ')',                                     0,                                     ')' ,                                     ', ' || c.data_scale || ')')),        c.DATA_TYPE) data_type  FROM cols c, obj o  WHERE c.TABLE_NAME = o.object_name    AND o.object_type = 'VIEW'       AND c.table_name LIKE '%PATTERN%'    ORDER BY c.table_name, c.column_id; 

Warning: This is incomplete with respect to multiple datatypes including char, varchar and timestamp and uses extremely old, deprecated dictionary views, back to oracle 5.

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 '_' 

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. In January 2006, EMM was available only through Oracle consulting services.

• Information schema
• Metadata

• article on Oracle Metadata