说我有一张这样的桌子
@H_301_1@id | device | cmd | value |
------+----------------+-------+---------
id = unique row ID
device = device identifier (mac address)
cmd = some arbitrary command
value = value of corresponding command
我想以某种方式自我加入此表以获取特定设备的特定cmds及其对应值.
我不想只是SELECT cmd,值FROM表WHERE device = ’00：11：22：33：44：55′;
假设我想要的值对应于getname和getlocation命令.我想输出类似的东西
@H_301_1@mac | name | location --------------------+-----------+------------ 00:11:22:33:44:55 | some name | somewhere我的sql fu很漂亮.我一直在尝试不同的组合,如SELECT a.value,b.value FROM table AS INNER JOIN表AS b ON a.device = b.device但我无处可去.
谢谢你的帮助.
@H_301_1@SELECT a.value AS thisval,b.value AS thatval
FROM table AS a JOIN table AS b USING (device)
WHERE a.command='this' AND b.command='that';
原文链接：https://www.f2er.com/postgresql/238879.html