在SQL Server 2012中,有一个Sales(订货信息)表,包含字段:warename(货品名称)和buyID(客户编号),统计出客户编号是1的订购不同货品数量。正确语句是
A.
SELECT count(*) FROM Sales where buyID=1;
B.
SELECT count(distinct warname) FROM Sales where buyID=1;
C.
SELECT distinct count(warname) FROM Sales where buyID=1;
D.
SELECT count(distinct warname) where buyID=1 FROM Sales;