具有唯一值的Mongodb过滤器结果
我有许多城市和邮政编码的集合，其中城市的名称可以相同，而邮政编码则不同。
例如，我试图查询以'San'开头的所有城市，并希望过滤结果，其中San Antonio仅与其他以San开头的城市一起出现。
这是我使用的代码：
Zipcodes.find(
{ city: { $regex: /San/, $options: 'i' } },
(err, result) => {
if (err) {
return res.send({ error: err });
}
res.send({ data: result });
},
).limit(20);
这给了我以下结果：
{
"loc": [
-94.132581,
31.515173
],
"_id": "75972",
"city": "SAN AUGUSTINE",
"pop": 5916,
"state": "TX"
},
{
"loc": [
-98.730929,
31.162678
],
"_id": "76877",
"city": "SAN SABA",
"pop": 4023,
"state": "TX"
},
{
"loc": [
-100.481752,
31.478165
],
"_id": "76901",
"city": "SAN ANGELO",
"pop": 23800,
"state": "TX"
},
{
"loc": [
-100.480036,
31.419411
],
"_id": "76904",
"city": "SAN ANGELO",
"pop": 25535,
"state": "TX"
},
{
"loc": [
-100.390005,
31.464738
],
"_id": "76905",
"city": "SAN ANGELO",
"pop": 11284,
"state": "TX"
},
{
"loc": [
-100.438586,
31.470735
],
"_id": "76903",
"city": "SAN ANGELO",
"pop": 32471,
"state": "TX"
},
{
"loc": [
-95.034496,
29.466033
],
"_id": "77539",
"city": "SAN LEON",
"pop": 21905,
"state": "TX"
},
{
"loc": [
-99.427148,
27.062523
],
"_id": "78067",
"city": "SAN YGNACIO",
"pop": 871,
"state": "TX"
},
{
"loc": [
-98.460127,
29.414799
],
"_id": "78203",
"city": "SAN ANTONIO",
"pop": 7261,
"state": "TX"
},
{
"loc": [
-98.525967,
29.422855
],
"_id": "78207",
"city": "SAN ANTONIO",
"pop": 58355,
"state": "TX"
},
{
"loc": [
-98.5063,
29.400217
],
"_id": "78204",
"city": "SAN ANTONIO",
"pop": 11526,
"state": "TX"
},
{
"loc": [
-98.479338,
29.441338
],
"_id": "78215",
"city": "SAN ANTONIO",
"pop": 1264,
"state": "TX"
},
{
"loc": [
-98.545219,
29.358366
],
"_id": "78211",
"city": "SAN ANTONIO",
"pop": 30417,
"state": "TX"
},
{
"loc": [
-98.492509,
29.423711
],
"_id": "78205",
"city": "SAN ANTONIO",
"pop": 1714,
"state": "TX"
},
{
"loc": [
-98.497511,
29.533387
],
"_id": "78216",
"city": "SAN ANTONIO",
"pop": 30435,
"state": "TX"
},
{
"loc": [
-98.419444,
29.539525
],
"_id": "78217",
"city": "SAN ANTONIO",
"pop": 27925,
"state": "TX"
}
它多次返回圣安东尼奥。我只需要一个。
请提供正确的查询帮助。谢谢。
回答如下：您可以使用$group + $replaceRoot来获得city唯一的值：
db.collection.aggregate([
{
$match: { city: { $regex: "San", $options: "i" } }
},
{
$group: {
_id: "$city",
doc: { $first: "$$ROOT" }
}
},
{
$replaceRoot: {
newRoot: "$doc"
}
}
])
Mongo Playground
具有唯一值的Mongodb过滤器结果
我有许多城市和邮政编码的集合，其中城市的名称可以相同，而邮政编码则不同。
例如，我试图查询以'San'开头的所有城市，并希望过滤结果，其中San Antonio仅与其他以San开头的城市一起出现。
这是我使用的代码：
Zipcodes.find(
{ city: { $regex: /San/, $options: 'i' } },
(err, result) => {
if (err) {
return res.send({ error: err });
}
res.send({ data: result });
},
).limit(20);
这给了我以下结果：
{
"loc": [
-94.132581,
31.515173
],
"_id": "75972",
"city": "SAN AUGUSTINE",
"pop": 5916,
"state": "TX"
},
{
"loc": [
-98.730929,
31.162678
],
"_id": "76877",
"city": "SAN SABA",
"pop": 4023,
"state": "TX"
},
{
"loc": [
-100.481752,
31.478165
],
"_id": "76901",
"city": "SAN ANGELO",
"pop": 23800,
"state": "TX"
},
{
"loc": [
-100.480036,
31.419411
],
"_id": "76904",
"city": "SAN ANGELO",
"pop": 25535,
"state": "TX"
},
{
"loc": [
-100.390005,
31.464738
],
"_id": "76905",
"city": "SAN ANGELO",
"pop": 11284,
"state": "TX"
},
{
"loc": [
-100.438586,
31.470735
],
"_id": "76903",
"city": "SAN ANGELO",
"pop": 32471,
"state": "TX"
},
{
"loc": [
-95.034496,
29.466033
],
"_id": "77539",
"city": "SAN LEON",
"pop": 21905,
"state": "TX"
},
{
"loc": [
-99.427148,
27.062523
],
"_id": "78067",
"city": "SAN YGNACIO",
"pop": 871,
"state": "TX"
},
{
"loc": [
-98.460127,
29.414799
],
"_id": "78203",
"city": "SAN ANTONIO",
"pop": 7261,
"state": "TX"
},
{
"loc": [
-98.525967,
29.422855
],
"_id": "78207",
"city": "SAN ANTONIO",
"pop": 58355,
"state": "TX"
},
{
"loc": [
-98.5063,
29.400217
],
"_id": "78204",
"city": "SAN ANTONIO",
"pop": 11526,
"state": "TX"
},
{
"loc": [
-98.479338,
29.441338
],
"_id": "78215",
"city": "SAN ANTONIO",
"pop": 1264,
"state": "TX"
},
{
"loc": [
-98.545219,
29.358366
],
"_id": "78211",
"city": "SAN ANTONIO",
"pop": 30417,
"state": "TX"
},
{
"loc": [
-98.492509,
29.423711
],
"_id": "78205",
"city": "SAN ANTONIO",
"pop": 1714,
"state": "TX"
},
{
"loc": [
-98.497511,
29.533387
],
"_id": "78216",
"city": "SAN ANTONIO",
"pop": 30435,
"state": "TX"
},
{
"loc": [
-98.419444,
29.539525
],
"_id": "78217",
"city": "SAN ANTONIO",
"pop": 27925,
"state": "TX"
}
它多次返回圣安东尼奥。我只需要一个。
请提供正确的查询帮助。谢谢。
回答如下：您可以使用$group + $replaceRoot来获得city唯一的值：
db.collection.aggregate([
{
$match: { city: { $regex: "San", $options: "i" } }
},
{
$group: {
_id: "$city",
doc: { $first: "$$ROOT" }
}
},
{
$replaceRoot: {
newRoot: "$doc"
}
}
])
Mongo Playground