Mybatis的关联关系的配置

例子1、

select * from t_key where lockid=#{id}

select * from t_key where id=#{id}

<!--
private Integer id;//钥匙的id
private String keyName;//钥匙的名
private Lock lock;//当前钥匙能开哪个锁；

id keyname lockid lid lockName
-->
select k.id,k.keyname,k.lockid, l.id lid,l.lockName from t_key k left join t_lock l on k.lockid=l.id where k.id=#{id}

例子2、

select * from t_lock where id=#{id}

<!--
update bs_book
set title=?,author=?,price=?,sales=?,stock=?,img_path=?
where id=?";

String sql = "update bs_book set";
if(employee.getTitle()){
sql+="title=?,"
}
if(){
sql + = "price=?,";
}
-->

select * from t_lock where id=#{id}

select l.*,k.id kid,k.keyname,k.lockid from t_lock l left join t_key k on l.id=k.lockid where l.id=#{id}

<!--
private Integer id;
private String lockName;
//查询锁子的时候把所有的钥匙也查出来
private List keys;

id lockName kid keyname lockid
3 303办公室的锁子 3 303钥匙1 3
3 303办公室的锁子 4 303钥匙2 3
3 303办公室的锁子 5 303钥匙3 3
-->