Oracle Data Dictionary

Reprint: http://www.itpub.net/thread-689020-1-1.html

An Oracle data dictionary is a database object that consists of tables and views that store information about the structure of the database. A database dictionary describes how the actual data is organized. They can be queried in the same way as other database tables or views, but cannot be modified.

Oracle's data dictionary is one of the most important parts of a database, which is generated as a result of database changes,
manifests as some tables and views under the SYS user. The data dictionary name is an uppercase English character.

Data dictionary contains user information, user's permission information, all data object information, table constraints, statistical analysis database view and so on.
We cannot manually modify the information in the data dictionary.

Many times, the average Oracle user does not know how to use it effectively.

Dictionary The name and interpretation of all data dictionary tables, it has a synonym dict
Dict_column All data dictionary table field names and explanations

If we want to query the data dictionary associated with the index, we can use the following SQL statement:

Sql>;select * from dictionary where InStr (comments, ' index ') >;0;

If we want to know the detailed meaning of each field name in the User_indexes table, you can use this SQL statement:

Sql>;select column_name,comments from Dict_columns where table_name= ' user_indexes ';

And so on, you can easily know the detailed name and explanation of the data dictionary without looking at other Oracle documentation.

The following is a list of the query usage methods for some Oracle user-common data dictionaries by category.

First, the user

View the default tablespace for the current user
Sql>;select username,default_tablespace from User_users;

View the role of the current user
Sql>;select * from User_role_privs;

View system and table-level permissions for the current user
Sql>;select * from User_sys_privs;
Sql>;select * from User_tab_privs;

Second, the table

View all the tables under the user
Sql>;select * from User_tables;

View a table with a name that contains a log character
Sql>;select object_name,object_id from User_objects
where InStr (object_name, ' LOG ') >;0;

To view the creation time of a table
Sql>;select object_name,created from User_objects where Object_name=upper (' &table_name ');

View the size of a table
Sql>;select sum (bytes)/(1024*1024) as "size (M)" from user_segments
where Segment_name=upper (' &table_name ');

View tables placed in Oracle's memory area
Sql>;select Table_name,cache from User_tables where InStr (Cache, ' Y ') >;0;

Third, index

View index number and category
Sql>;select Index_name,index_type,table_name from User_indexes ORDER by TABLE_NAME;

View the fields indexed by the index
Sql>;select * from User_ind_columns where Index_name=upper (' &index_name ');

To view the size of an index
Sql>;select sum (bytes)/(1024*1024) as "size (M)" from user_segments
where Segment_name=upper (' &index_name ');

Four, serial number

View serial number, Last_number is the current value
Sql>;select * from User_sequences;

V. views

View the name of the view
Sql>;select view_name from User_views;

View the SELECT statement that created the view
Sql>;set view_name,text_length from User_views;
Sql>;set Long 2000; Description: The size of the set long can be set according to the Text_length value of the view
Sql>;select text from User_views where View_name=upper (' &view_name ');

Vi. synonyms

View the name of a synonym
Sql>;select * from user_synonyms;

Vii. Conditions of constraint

View constraints on a table
Sql>;select constraint_name, Constraint_type,search_condition, R_constraint_name
From user_constraints WHERE table_name = UPPER (' &table_name ');

Sql>;select C.constraint_name,c.constraint_type,cc.column_name
From User_constraints c,user_cons_columns cc
where C.owner = Upper (' &table_owner ') and c.table_name = Upper (' &table_name ')
and C.owner = Cc.owner and c.constraint_name = Cc.constraint_name
Order BY Cc.position;

VIII. Storage functions and procedures

View the status of functions and procedures
Sql>;select object_name,status from user_objects where object_type= ' FUNCTION ';
Sql>;select object_name,status from user_objects where object_type= ' PROCEDURE ';

View source code for functions and procedures
Sql>;select text from All_source where Owner=user and Name=upper (' &plsql_name ');