CREATE TABLE EMP2 AS SELECT * FROM EMP WHERE 1=2;--只复制表结构CREATE TABLE TEST1 AS SELECT EMPNO,ENAME,JOB,SAL FROM EMP WHERE DEPTNO=10;--只复制另一个表中的某几个字段CREATE TABLE EMP2 AS SELECT * FROM EMP; --复制整张表，包括数据CREATE TABLE EMP2 AS SELECT * FROM EMP WHERE rownum<=10;--只复制前10行数据

INSERT INTO DEPT VALUES(50,‘DBA‘,‘HK‘);--所有字段都插入值INSERT INTO DEPT(DEPTNO,DNAME) VALUES(60,‘TEST‘);--只插入其中几个字段值INSERT INTO EMP2 (SELECT * FROM EMP);--使用子查询插入数据时，不要加values或asINSERT INTO EMP2 (SELECT * FROM EMP WHERE ROWNUM<=10);

update emp2 set empno=2222,ename=‘rusky‘ where empno=1111;--如果不加where条件，则更新表中的所有行。update emp2 set (empno,ename)=(2222,‘rusky‘) where empno=1111;--ORA-01767: UPDATE ...SET 表达式必须是子查询 update emp2 set (ename,job,hiredate)=(select ename,job,hiredate from emp where empno=7369) where empno=1111;--使用子查询修改表DELETE FROM TEST1 WHERE EMPNO=7782;--删除表中的某一行记录DELETE FROM TEST;--不加WHERE条件，清空表中所有记录DELETE FROM EMP2 WHERE DEPTNO=(SELECT DEPTNO FROM DEPT WHERE DNAME=‘SALES‘); --使用子查询删除记录

ALTER TABLE DEPT2 ADD (MANAGER NUMBER(4)); --增加列ALTER TABLE DEPT2 MODIFY(MANAGER NUMBER(4));--修改列属性ALTER TABLE DEPT2 DROP COLUMN MANAGER;--删除表中的字段DROP TABLE DEPT2;--直接删除表，包括表数据和表结构。TRUNCATE TABLE DEPT2;--只清空表中的数据RENAME DEPT2 TO DEPT3;--修改表名COMMENT ON TABLE DEPT3 IS ‘THIS IS A TEST TABLE‘; --给表增加注释COMMENT ON COLUMN DEPT3.MANAGER IS ‘THE MANAGER OF THIS DEPARTMENT‘;--给某个字段增加注释

SELECT * FROM USER_TABLES; --查看用户所有表SELECT DISTINCT OBJECT_TYPE FROM USER_OBJECTS; --查看用户拥有的数据类型SELECT * FROM USER_CATALOG; --查看用户拥有的表、视图、同义词、序列查看表、字段、视图、同义词等的注释：ALL_COL_COMMENTSUSER_COL_COMMENTSALL_TAB_COMMENTSUSER_TAB_COMMENTS

CREATE TABLE Goods(GoodsId char(8) primary key, --主键GoodName varchar2(50),UnitPrice number(10,2) check(UnitPrice>0),--单价必须大于0Category varchar2(30),Provider varchar2(100));--添加注释COMMENT ON TABLE Goods is ‘ 商品表Goods（商品号GoodsId，商品名GoodName，单价UnitPrice，商品类别Categroy，供应商Provider）‘CREATE TABLE Customers(CustomerId char(8) primary key, --主键Name varchar2(30) not null,--姓名允许为空Address varchar2(150),Email varchar2(100) unique, --Email唯一Gender char(2) default(‘男‘) check(Gender in(‘男‘,‘女‘)), --性别只能是男或女CardId char(18));--添加注释COMMENT ON TABLE Customers is ‘客户表Customers（客户号CustomerId，姓名Name，住址Address，电邮Email，性别Gender，身份证CardId）‘CREATE TABLE Purchases(CustomerId char(8) references Customers(Customerid), --外键GoodId char(8) references Goods(GoodsId),Num number(10) check(Num between 1 and 30));--添加注释COMMENT ON TABLE Purchases is ‘销售表Purchases（客户号CustomerId，商品号GoodsId，购买数量Num）‘

sql> create table Goods(GoodsId char(8),GoodsName varchar2(50), Category varchar(30),constraint PK_GoodsId primary key(GoodsId));

sql>create table Goods(GoodsId char(8) constraint PK_GoodsId primary key ,--主键GoodName varchar2(50),UnitPrice number(10,2) check(UnitPrice>0),--单价必须大于0Category varchar(30),Provider varchar(100));

ALTER TABLE Goods modify GoodsId not null;ALTER TABLE Customers add constraint UQ_CardId unique(Cardid);

sql>alter table 表名 drop constraint 约束名称;ALTER TABLE Customers drop constraints UQ_CardId;

ALTER TABLE EMPLOYEE RENAME CONSTRAINT PK_EMPLOYEE TO PK_EMPLOYEE1;

列级定义约束：CREATE TABLE DEPARTMENT(DEPTID NUMBER(2) PRIMARY KEY,--或者DEPTID NUMBER(2) CONSTRAINT PK_DEPARTMENT PRIMARY KEY,NAME VARCHAR2(12),LOC VARCHAR2(12));表级定义约束：CREATE TABLE EMPLOYEE(EMPID NUMBER(4),NAME VARCHAR2(10),DEPTID NUMBER(2),CONSTRAINT PK_EMPLOYEE PRIMARY KEY(EMPID),CONSTRAINT FK_DEPARTMENT FOREIGN KEY(DEPTID) REFERENCES DEPARTMENT(DEPTID));

CREATE TABLE DEPARTMENT2(DEPTID NUMBER(2),--或者DEPTID NUMBER(2) CONSTRAINT PK_DEPARTMENT PRIMARY KEY,DNAME VARCHAR2(12),LOC VARCHAR2(12),PRIMARY KEY(DEPTID,DNAME));CREATE TABLE EMPLOYEE2(EMPID NUMBER(4) PRIMARY KEY,NAME VARCHAR2(10),DEPTID NUMBER(2),DNAME VARCHAR2(12),CONSTRAINT FK_DEPARTMENT1 FOREIGN KEY(DEPTID,DNAME) REFERENCES DEPARTMENT2(DEPTID,DNAME) ON DELETE CASCADE--当删除部门表中的某个部门信息时，级联删除员工表中的 DEPTNO,DNAME.或者这样：ON DELETE SET NULL，设为null);