Oracle SQL Plus The Definitive Guide- P22:Every day, computer professionals the world over wake up, travel to the office, sit down in front of a computer, and begin another day working with that database called Oracle. Programmers write queries and stored procedures. Database administrators monitor performance, make database changes, and perform other maintenance tasks. Operations people may need to back up or recover a database. | table continued on next page previous page page_185 next page previous page page_186 next page Page 186 Table 6-3. Columns in the ALL TAB COLUMNS View continued Column Name Contents SAMPLE_SIZE The number of rows that were sampled when statistics were last computed for this CHARACTER_SET_NAME For character columns this indicates which character set is stored by the column. This value will be either NCHAR_CS or CHAR_CS. NCHAR_CS indicates that data in the column is stored using the national character set. CHAR_CS indicates that the database character set is used. a Not maintained automatically by Oracle beginning with Oracle8 you should use the ALL_TAB_COL_STATISTICS view to retrieve this value. This column is set when you use the ANALYZE TABLE command with the COMPUTE STATISTICS option. b Not maintained automatically by Oracle. This column is set when you use the ANALYZE TABLE command with the COMPUTE STATISTICS option. The ALL CONSTRAINTS view The ALL_CONSTRAINS view returns one row for each constraint you can see. Oracle will let you see all constraints on tables you own as well as all constraints on tables to which you have been granted any type of access. Table 6-4 lists the columns in this view. Table 6-4. Columns in the ALL CONSTRAINTS View Column Name Contents OWNER The owner of the constraint. This is usually the same as the owner of the table on which the constraint is defined. CONSTRAINT_NAME The name of the constraint. CONSTRAINT_TYPE Indicates the type of constraint. Will be one of these values P PRIMARY KEY R FOREIGN KEY C CHECK U UNIQUE KEY TABLE_NAME The table on which the constraint is defined. SEARCH_CONDITION If the constraint is a check constraint this is the condition that must be satisfied for each row stored in the table. For other constraint types this will be null. R_OWNER For foreign key constraints this is the owner of the related primary key or unique constraint. R_CONSTRAINT_NAME For foreign key constraints this is the related
