To implement string comparison in MongoDB, use $strcasecmp. It performs case-insensitive comparison of two strings. It returns −
1 if first string is “greater than” the second string.
0 if the two strings are equal.
-1 if the first string is “less than” the second string.
Let us create a collection with documents −
> db.demo490.insertOne({"Name1":"John","Name2":"john"});{ "acknowledged" : true, "insertedId" : ObjectId("5e8496ccb0f3fa88e22790bb") } > db.demo490.insertOne({"Name1":"David","Name2":"Bob"});{ "acknowledged" : true, "insertedId" : ObjectId("5e8496d9b0f3fa88e22790bc") } > db.demo490.insertOne({"Name1":"Carol","Name2":"Carol"});{ "acknowledged" : true, "insertedId" : ObjectId("5e8496e5b0f3fa88e22790bd") }
Display all documents from a collection with the help of find() method −
> db.demo490.find();
This will produce the following output −
{ "_id" : ObjectId("5e8496ccb0f3fa88e22790bb"), "Name1" : "John", "Name2" : "john" } { "_id" : ObjectId("5e8496d9b0f3fa88e22790bc"), "Name1" : "David", "Name2" : "Bob" } { "_id" : ObjectId("5e8496e5b0f3fa88e22790bd"), "Name1" : "Carol", "Name2" : "Carol" }
Following is the query to implement string comparison in MongoDB −
> db.demo490.aggregate( ... [ ... { ... $project: ... { ... Name1: 1, ... Name2: 1, ... Result: { $strcasecmp: [ "$Name1", "$Name2" ] } ... } ... } ... ] ... )
This will result the following output −
{ "_id" : ObjectId("5e8496ccb0f3fa88e22790bb"), "Name1" : "John", "Name2" : "john", "Result" : 0 } { "_id" : ObjectId("5e8496d9b0f3fa88e22790bc"), "Name1" : "David", "Name2" : "Bob", "Result" : 1 } { "_id" : ObjectId("5e8496e5b0f3fa88e22790bd"), "Name1" : "Carol", "Name2" : "Carol", "Result" : 0 }