select distinct a.id,a.name,a.pid from AA as a, AA as b where a.pid=b.id;
最后怎么获取值啊,都用rs.getString("name")吗?
你可以用rs.getString(1);这种方式, 你也可以这样写sql语句,用rs.getString("name") select distinct a.id as id,a.name as name,a.pid as pid from AA as a, AA as b where a.pid=b.id;
问题是这样的,我需要得到 id 所在的name值 同时还要得到 pid 所在的name值关键问题在这。。 我用了一个分页程序如果每获取一次pid然后再到库中查询 很耗内存...所以想知道怎么解决这个问题?
select distinct a.id as id,a.name as name,a.pid as pid ,b.name as pname from AA as a, AA as b where a.pid=b.id;rs.getString("pname");
有两个表: AA id name author 1 文本 1 2 数据 1 3 代码 0 4 HTML 2BB id name 1 san 2 wang 3 niu 请问如何列出这种效果,数据库是MYSQL1 文本 san 2 数据 san 3 代码 未知 4 HTML wang请问这种效果如何实现
select distinct a.id as id,a.name as name,a.author as author ,b.name as bname from AA as a, BB as b where a.author=b.id;
select distinct a.id as id,a.name as name,a.author as author ,b.name as bname from AA as a left join BB as b where a.author=b.id;==================== 这回你试试,好久不做,外联忘的差不多了
select aa.id, aa.name, (select bb.name from BB as bb where aa.author=bb.id) from AA as aa;
这个是最付合你的 select aa.id, aa.name,ifnull((select bb.name from BB as bb where aa.author=bb.id),'未知') from AA as aa;
你也可以这样写sql语句,用rs.getString("name")
select distinct a.id as id,a.name as name,a.pid as pid from AA as a, AA as b where a.pid=b.id;
我用了一个分页程序如果每获取一次pid然后再到库中查询 很耗内存...所以想知道怎么解决这个问题?
AA
id name author
1 文本 1
2 数据 1
3 代码 0
4 HTML 2BB
id name
1 san
2 wang
3 niu
请问如何列出这种效果,数据库是MYSQL1 文本 san
2 数据 san
3 代码 未知
4 HTML wang请问这种效果如何实现
这回你试试,好久不做,外联忘的差不多了
select aa.id, aa.name,ifnull((select bb.name from BB as bb where aa.author=bb.id),'未知') from AA as aa;