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+----+-----------+---------+ | id | name | dept_id | +----+-----------+---------+ | 6 | Dennis-6 | NULL | | 7 | Dennis-7 | NULL | | 8 | Dennis-8 | NULL | | 9 | Dennis-9 | NULL | | 10 | Dennis-10 | NULL | +----+-----------+---------+ # 把 table emp_dept 放在左边的情形(当然以 emp_dept 中的数据为基础来显示资料,emp 中比emp_dept 中多的资料也就不会显示出来了): select a.id,a.name,b.dept_id from emp_dept b left join emp a on (a.id=b.emp_id); mysql> select a.id,a.name,b.dept_id -> from emp_dept b left join emp a on (a.id=b.emp_id); +------+----------+---------+ | id | name | dept_id | +------+----------+---------+ | 2 | Dennis-2 | DEv | | 1 | Dennis-1 | R&D | | 3 | Dennis-3 | R&D | | 4 | Dennis-4 | Test | | 5 | Dennis-5 | Test | +------+----------+---------+ >> right join --------------- select a.id,a.name,b.dept_id from emp a right join emp_dept b on (a.id=b.emp_id); # 挑资料时以右边 table emp_dept 中的资料为基础来显示资料 mysql> select a.id,a.name,b.dept_id -> from emp a right join emp_dept b on (a.id=b.emp_id);
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正在阅读：数据库学习:MySQL Join详解数据库学习:MySQL Join详解
2004-04-01 13:26
出处：CSDN
责任编辑：linjixiong
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