oracle系统表

类一.user_XXX ：当前用户的系统视图
1.user_tables:当前用户的所有表
2.user_constraints：当前用户的表约束
SQL> desc user_constraints;
Name              Type         Nullable Default Comments                                                                   
----------------- ------------ -------- ------- ---------------------------------------------------------------------------
OWNER             VARCHAR2(30)                  Owner of the table                                                         
CONSTRAINT_NAME   VARCHAR2(30)                  Name associated with constraint definition                                 
CONSTRAINT_TYPE   VARCHAR2(1)  Y                Type of constraint definition                                              
TABLE_NAME        VARCHAR2(30)                  Name associated with table with constraint definition                      
SEARCH_CONDITION  LONG         Y                Text of search condition for table check                                   
R_OWNER           VARCHAR2(30) Y                Owner of table used in referential constraint                              
R_CONSTRAINT_NAME VARCHAR2(30) Y                Name of unique constraint definition for referenced table                  
DELETE_RULE       VARCHAR2(9)  Y                The delete rule for a referential constraint                               
STATUS            VARCHAR2(8)  Y                Enforcement status of constraint -  ENABLED or DISABLED                    
DEFERRABLE        VARCHAR2(14) Y                Is the constraint deferrable - DEFERRABLE or NOT DEFERRABLE                
DEFERRED          VARCHAR2(9)  Y                Is the constraint deferred by default -  DEFERRED or IMMEDIATE             
VALIDATED         VARCHAR2(13) Y                Was this constraint system validated? -  VALIDATED or NOT VALIDATED        
GENERATED         VARCHAR2(14) Y                Was the constraint name system generated? -  GENERATED NAME or USER NAME   
BAD               VARCHAR2(3)  Y                Creating this constraint should give ORA-02436.  Rewrite it before 2000 AD.
RELY              VARCHAR2(4)  Y                If set, this flag will be used in optimizer                                
LAST_CHANGE       DATE         Y                The date when this column was last enabled or disabled                     
INDEX_OWNER       VARCHAR2(30) Y                The owner of the index used by the constraint                              
INDEX_NAME        VARCHAR2(30) Y                The index used by the constraint                                           
INVALID           VARCHAR2(7)  Y                                                                                           
VIEW_RELATED      VARCHAR2(14) Y

3.user_cons_columns ：是表约束字段的视图,说明表中的和约束相关的列参与了哪些约束。这些约束有主键约束,外键约束,索引约束
desc user_cons_columns;
Name            Type           Nullable Default Comments                                                                                        
--------------- -------------- -------- ------- ------------------------------------------------------------------------------------------------
OWNER           VARCHAR2(30)                    Owner of the constraint definition                                                              
CONSTRAINT_NAME VARCHAR2(30)                    Name associated with the constraint definition                                                  
TABLE_NAME      VARCHAR2(30)                    Name associated with table with constraint definition                                           
COLUMN_NAME     VARCHAR2(4000) Y                Name associated with column or attribute of object column specified in the constraint definition
POSITION        NUMBER         Y                Original position of column or attribute in definition