mysql高级查询

1 两个table 的数据price做差，输出价差。输出到文件，默认空格分隔符。由于time中秒数有的不为0，所以要小时相等、分钟相等。2.8W数据查询耗时90秒。

select m1905.date,m1905.time, y1905.cprice - m1905.cprice*2 from m1905,y1905 where m1905.date=y1905.date and minute(m1905.time)=minute(y1905.time) and hour(m1905.time)=hour(y1905.time) order by m1905.row_id into outfile '/var/lib/mysql-files/y_m2.csv';