postgre数据库如何实现行转列
create table t(day date,equipment varchar(20),output integer);
insert into t values('2010-04-01','DAT501',100);
insert into t values('2010-04-01','DAT502',120);
insert into t values('2010-04-01','DAT503',130);
insert into t values('2010-04-02','DAT501',110);
insert into t values('2010-04-02','DAT502',105);
insert into t values('2010-04-03','DAT503',125);
insert into t values('2010-04-04','DAT501',100);
insert into t values('2010-04-04','DAT503',200);
--想得到如下结果
day | dat501 | dat502 | dat503
----------------+-----------+----------+--------
2010-04-01 | 100 | 120 | 130
2010-04-02 | 110 | 105 |
2010-04-03 | | | 125
2010-04-04 | 100 | | 200