Needless to say, mongodb also support to sort data. THe positive one means sorting by asc order and negetive means by desc.
The grammar of group:
Description Of Argument:
key： The field need to group
cond: query condition
Initial: initialize the counter of group
Redue: generally statistic operation
Finalize: further operation after group, for exampe calcuate the average.
3.
it‘s the same as the distinct in the relational database.
The mongodb supports to use skip and limit to query by page.
【MongoDB】The high query operation of MongoDB（三）
原文：http://blog.csdn.net/sxb0841901116/article/details/39484093
