How to say… match when field is a number… in mongodb?

Question

So I have a field called \'city\' in my results...the results are corrupted, some times it\'s an actual name, sometimes it\'s a number. The following code displays all the recor

Answer 1

An easier way to match all docs where city is a numeric string is using the property '0' <= city <= '9' i.e. your aggregation query becomes:

db.zips.aggregate([
    {$project : {city:{$substr:["$city",0,1]}}},
    {$sort : {city : 1}}, 
    {$match: {city: {$gte: '0', $lte: '9'}}}
]);

When using JohnnyHK's suggestion of a regex you can save yourself the $project stage altogether.

Answer 2

Simply use:

db.zips.aggregate([
{$match: {
    'city': { $regex: '^[0-9].*'}
}}])

This work fine for me!

Answer 3

You can also use an in command

db.zips.aggregate([     
    {
        $project: {
            first_char: { 
                $substr : ["$city",0,1]
            }, 
            "_id":"$_id"
        } 
    }, 
    {
        $match: {
            first_char: { 
                $in: ["0","1","2","3","4","5","6","7","8","9"] 
            }
        }
    }
]) 

Answer 4

Use the $type operator in your $match:

db.zips.aggregate([
    {$project : {city:{$substr:["$city",0,1]}}},
    {$sort : {city : 1}}, 
    {$match: {city: {$type: 16}}}      // city is a 32-bit integer
]);

There isn't a single type value for number so you need to know which type of number you have:

32-bit integer   16
64-bit integer   18
Double           1

Or use an $or operator to match all types of numbers:

db.zips.aggregate([
    {$project : {city:{$substr:["$city",0,1]}}},
    {$sort : {city : 1}}, 
    {$match: {$or: [{city: {$type: 1}}, {city: {$type: 16}}, {city: {$type: 18}}]}}
]);

Or even use $not to match all docs where city is not a string:

db.zips.aggregate([
    {$project : {city:{$substr:["$city",0,1]}}},
    {$sort : {city : 1}}, 
    {$match: {city: {$not: {$type: 2}}}}      // city is not a string
]);

UPDATED

To match all docs where city is a numeric string you can use a regular expression:

db.zips.aggregate([
    {$project : {city:{$substr:["$city",0,1]}}},
    {$sort : {city : 1}}, 
    {$match: {city: /^\d.*$/}}      // city is all digits
]);

Answer 5

db.zips.aggregate([
    {$project : {city:{$substr:["$city",0,1]},pop:1}},
    {$group:{_id:"$city",sumPop:{$sum:"$pop"}}},
    {$sort : {_id : 1}}, 
    {$match:{_id : {$regex:/\d/}} },
    {$group:{_id:"id",sumPop:{$sum:"$sumPop"}}},
]);

Answer 6

Why not to use $regex?

db.zips.aggregate([
    {$project : {city:{$substr:["$city",0,1]}}},
    {$sort : {city : 1}}, 
    {$match: {city:{$regex:'[0-9]'}}}
])