查询用户下所有表:select * from tab;
删除表: drop table 表名;
但是删除表后还是会查询到BIN开头的垃圾表,drop后的表存在于回收站:
清空回收站所有表: purge recyclebin;
打开/创建文本: ed 文件名.sql
执行文本脚本: @ 文件名.sql
创建表(创主键):
create table company(
cid number() primary key,
cname varchar2(20) not null
);
创建表(创复合主键):
create table company(
cid number(11),
cname varchar2(20) not null,
constraint pk_company primary key(cid)
);
创建表(创外键):
create table emp(
eid number(11) primary key,
ename varchar2(20) not null,
cid number() references company(cid)
);
创建表(创复合外键):
create table emp(
eid number(11) not null,
ename varchar2(20) not null,
cid number(11),
constraint pk_emp primary key(eid),
constraint fk_emp_company foreign key(cid) references company(cid)
);
左外连接与又外连接语法: select * from A表 right/left outer join B表 on A.字段 = B.字段;
说明: 若是left则以左边的表为基准,若是right则以右边的表为基准。
select * from emp e right outer join company c on e.CID = c.CID;
select * from emp e left outer join company c on e.CID = c.CID;
select * from company c left outer join emp e on e.CID = c.CID;
select * from company c right outer join emp e on e.CID = c.CID;