創建一張表包含非空約束，唯一約束和check約束

SQL> create table dept(
2 ename varchar2(20) constraint mep_ename_nn not null,
3 email varchar2(30) constraint mep_email_uk unique,
4 constraint emp_email_ck check ((instr(email,[email protected])>0)));

Table created.

查看約束情況：
SQL> select constraint_name,constraint_type,column_name
2 from user_constraints natural join user_cons_columns
3 where table_name=‘DEPT‘;

CONSTRAINT_NAME C COLUMN_NAME
------------------------------ - ---------------
MEP_ENAME_NN C ENAME
EMP_EMAIL_CK C EMAIL
MEP_EMAIL_UK U EMAIL

使用create table as語句創建另外一張表：

SQL> create table dept_test as select * from dept;

Table created.

檢查約束情況，只有ename上的nut null約束被復制了過來

SQL> select constraint_name,constraint_type,column_name
2 from user_constraints natural join user_cons_columns
3 where table_name=‘DEPT_TEST‘;

CONSTRAINT_NAME C COLUMN_NAME
------------------------------ - ---------------
SYS_C0011591 C ENAME

嘗試插入數據報錯

SQL> insert into dept_test(email) values([email protected]