【单选题】There is been competition between the two Motor car firms.
【简答题】假设同一名称的产品有不同的型号和产地,则计算每种产品平均单价的SQL语句是( )。 A)SELECT产品名称,AVG(单价)FROM 产品 GROUPBY 单价 B)SELECT产品名称,AVG(单价)FROM 产品 0RDERBY 单价 C)SELECT产品名称,AVG(单价)FROM 产品 0RDERBY 产品名称 D)SELECT产品名称,AVG(单价)FROM 产品 GROUPBY 产品名...
【单选题】如果学生表中有“所在系”字段,可用SQL语句______来统计全校有多少个系。
B.
SELECTSUM(DISTINCT所在系)
D.
SELECTCOUNT(DISTINCT所在系)
【简答题】入户电缆YJV22- 4*16的工程量是()m
【判断题】Demurrage is the extra charge a shipper pays for detaining a freight car or ship beyond time permitted for loading or unloading.