How to replace SQL concatenation in mongoDB
example in SQL:
SELECT CONCAT(firstName, ” “, lastName) AS fullName
FROM Customers WHERE concat(firstName, " ", lastName) = 'value'
;
MongoDB:
in below 3.6
db.coll.aggregate({$match:{firstName:/^val/}},
{$project:{newField:{$concat:["$firstName","$lastName"]}}},
{$match:{newField:"value"}}
);
please consider to index firstName, wich will improve performance .
in 3.6 or above :
db.coll.find({$expr:{$eq:["value", {$concat:["$firstName", "$lastName"]}]}})