In MongoDB, how do you retrieve a set of results where Field X is greater than Field Y by Value N?












1














I'm trying to query my local MongoDB for documents where Field X is greater than Field Y by Value N (in this case, Value N = 0.25).



I currently have:



db.getCollection('collection1').find({ $expr: { $gt: [ "$field1" , "$field2" ] }}).sort({"dateAdded" : -1})


But this only returns results where field1 is greater than field2. I need field1 to be greater than field2 by 0.25.



I can't find this in the documentation anywhere, i'm sure i'm missing something easy...



Thanks for your help.










share|improve this question



























    1














    I'm trying to query my local MongoDB for documents where Field X is greater than Field Y by Value N (in this case, Value N = 0.25).



    I currently have:



    db.getCollection('collection1').find({ $expr: { $gt: [ "$field1" , "$field2" ] }}).sort({"dateAdded" : -1})


    But this only returns results where field1 is greater than field2. I need field1 to be greater than field2 by 0.25.



    I can't find this in the documentation anywhere, i'm sure i'm missing something easy...



    Thanks for your help.










    share|improve this question

























      1












      1








      1


      1





      I'm trying to query my local MongoDB for documents where Field X is greater than Field Y by Value N (in this case, Value N = 0.25).



      I currently have:



      db.getCollection('collection1').find({ $expr: { $gt: [ "$field1" , "$field2" ] }}).sort({"dateAdded" : -1})


      But this only returns results where field1 is greater than field2. I need field1 to be greater than field2 by 0.25.



      I can't find this in the documentation anywhere, i'm sure i'm missing something easy...



      Thanks for your help.










      share|improve this question













      I'm trying to query my local MongoDB for documents where Field X is greater than Field Y by Value N (in this case, Value N = 0.25).



      I currently have:



      db.getCollection('collection1').find({ $expr: { $gt: [ "$field1" , "$field2" ] }}).sort({"dateAdded" : -1})


      But this only returns results where field1 is greater than field2. I need field1 to be greater than field2 by 0.25.



      I can't find this in the documentation anywhere, i'm sure i'm missing something easy...



      Thanks for your help.







      database mongodb expression robo3t






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      asked Dec 28 '18 at 9:36









      Ruben MurrayRuben Murray

      61




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          1 Answer
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          Create an expression that calculates the difference first and then you can do the greater than comparison.



          Take for instance this query which uses the $subtract operator to get the difference:



          db.getCollection('collection1').find(
          { "$expr": {
          "$gt": [
          { "$subtract": ["$field1", "$field2"] },
          0.25
          ]
          }}
          ).sort({"dateAdded" : -1})





          share|improve this answer





















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            1 Answer
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            active

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            1














            Create an expression that calculates the difference first and then you can do the greater than comparison.



            Take for instance this query which uses the $subtract operator to get the difference:



            db.getCollection('collection1').find(
            { "$expr": {
            "$gt": [
            { "$subtract": ["$field1", "$field2"] },
            0.25
            ]
            }}
            ).sort({"dateAdded" : -1})





            share|improve this answer


























              1














              Create an expression that calculates the difference first and then you can do the greater than comparison.



              Take for instance this query which uses the $subtract operator to get the difference:



              db.getCollection('collection1').find(
              { "$expr": {
              "$gt": [
              { "$subtract": ["$field1", "$field2"] },
              0.25
              ]
              }}
              ).sort({"dateAdded" : -1})





              share|improve this answer
























                1












                1








                1






                Create an expression that calculates the difference first and then you can do the greater than comparison.



                Take for instance this query which uses the $subtract operator to get the difference:



                db.getCollection('collection1').find(
                { "$expr": {
                "$gt": [
                { "$subtract": ["$field1", "$field2"] },
                0.25
                ]
                }}
                ).sort({"dateAdded" : -1})





                share|improve this answer












                Create an expression that calculates the difference first and then you can do the greater than comparison.



                Take for instance this query which uses the $subtract operator to get the difference:



                db.getCollection('collection1').find(
                { "$expr": {
                "$gt": [
                { "$subtract": ["$field1", "$field2"] },
                0.25
                ]
                }}
                ).sort({"dateAdded" : -1})






                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered Dec 28 '18 at 10:05









                chridamchridam

                66.3k13105138




                66.3k13105138






























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