Question

两表关联查询SQL语句的，要怎么写？

Answer 1

1、创建测试表；

create table company(companyId number, companyName varchar2(20), contacts varchar2(20));

create table users(userId number, companyId number, userName varchar2(20), userAge number, address varchar2(20));

2、插入测试数据；

insert into company values (1,'腾讯科技','马化腾');

insert into company values (2,'微软公司','鲍威尔');

insert into company values (3,'新浪科技','小明' );

insert into users values (1,1,'jack',23 , '上海'); 

insert into users values (2,1,'jack2', 23, '上海'); 

insert into users values (3,2,'jack3', 23, '上海'); 

insert into users values (4,2,'jack4', 23, '上海'); 

insert into users values (5,3,'jack5', 23, '上海'); 

insert into users values (6,3,'jack6', 23, '上海'); 

3、查询表中数据；

select * from users;

4、编写sql，关联两张表；select * from users t , company b where t.companyid = b.companyid and t.companyid = 1;