// 準(zhǔn)備測試數(shù)據(jù)
db.user.drop();
for(var i=10; i 100; i++) {
db.user.insert({
name:"user" + i,
age : Math.floor(Math.random()*10)+ 20,
sex : Math.floor(Math.random()*3)%2 ==0 ? 'M' : 'F',
chinese : Math.floor(Math.random()*50)+50,
math : Math.floor(Math.random()*50)+50,
english : Math.floor(Math.random()*50)+50,
class : "C" + i%5
})
}
// group函數(shù)
// 按照class進(jìn)行分組，顯示每個class中的用戶姓名和性別
db.user.group({
key: {"class": true},
initial: {"person": []},
reduce: function(cur, prev) {
prev.person.push({name: cur.name, sex: cur.sex, age: cur.age});
}
});
// 對age>25的用戶，按照class進(jìn)行分組，顯示每個class中的用戶姓名和性別，并統(tǒng)計每組的人數(shù)
db.user.group({
key: {"class": true},
initial: {"person": []},
reduce: function(doc, out){
out.person.push({name: doc.name, sex: doc.sex, age: doc.age});
},
finalize: function(out){
out.count = out.person.length;
},
condition: {"age": {$gt: 25}}
})
// 分組計算每個class中，chinese最大值和最小值
db.user.group({
key: {"class": true},
initial: {"chinese_min": 0, "chinese_max":0 },
reduce: function(doc, out){
out.chinese_min = doc.chinese;
out.chinese_min = doc.chinese;
out.chinese_min = Math.min(out.chinese_min, doc.chinese);
out.chinese_max = Math.max(out.chinese_max, doc.chinese)
},
})
// 利用分組，計算每個總成績和成績平均值
db.user.group({
key: {"_id" : true},
initial: {name:"", total: 0, avg: 0},
reduce: function(doc, out){
out.name = doc.name;
out.total = doc.chinese + doc.math + doc.english;
out.avg = Math.floor(out.total / 3);
}
})
