各位大侠，我有如下一段程序，目的是从一个数据框df 中提取part_num="P0001" 的数据，但应该如何在P0001上加是个" "呢？？
感谢帮助！
> sql_str<-paste('select part_num as part_num,ord_lt as lt from df where part_num==',as.character(order_behave[1,1]))
> sql_str
[1] "select part_num as part_num,ord_lt as lt from df where part_num== P0001"
> sqldf(sql_str)
错误: no such column: P0001