SQL聚合函数中包含计算,列数据属性非数据格式则计算结果出错
在mysql中,同样在聚合函数中进行单位缩减,如果duration是varchar,计算会出错,duration是int就没问题
1 SELECT departure_city,SUM(duration) AS 'SUM' 2 FROM `bus_route` 3 GROUP BY departure_city; 4 5 SELECT departure_city,SUM(duration/1000) AS 'SUM' 6 FROM `bus_route` 7 GROUP BY departure_city;