VB多表分组统计，读取Access数据库，通过查询统计图书的销售数量和现存数量来演示分组统计数据，书号,k.书名,x.作者, k.现存数量 ,sum(x.销售数量)as 销售数量。-The VB group multi-table statistics, read the Access database to demonstrate, through the query statistics book sales number and the number of existing packet