datatable A
id     name    type   count
1        甲          A          10
2        乙          A           8
3        丙          B           6
datatable B
id     name    type   count
1        甲          A          9
2        乙          A          7
3        丙          B          5
4        丁          B          3
两个这样列相同的datatable ，同样 id和 type的 count 列 的行之间高效比较。得出count列的不同值