"ORACLE" SQL statement simple Application (v) (11g)

Not NULL non-null field +not null

Unique only

Primary key primary key (ensure data cannot be duplicated)

FOREIGN key foreign key

Check must

Drop purge completely removed

Cascade Delete: Delete A department, the staff in the department then delete the --->on delete cascade

Empty: Transfer employees from the department to Null, delete Department --->on delete set null

Cannot move: Delete the employee first, then delete the department

References Reference

Constraint constraints

tables created with subqueries in addition to null, constraints cannot be copied

Col first_name for A10

Read only: can only query, no additions and deletions (readonly) unlock read only

where 1=2; do not copy table contents

Increment by each add value

Start with from where

MaxValue added to maximum value

Nocycle Cycle

NoCache put the serial number into memory.

Modify in Index: Delete and insert first

"ORACLE" SQL statement simple Application (v) (11g)