$concat
Reference group: String aggregation expressions
What it does
Concatenates strings; null inputs can yield null, so use $ifNull when needed.
Syntax
{$concat: [stringExpr, ...]}
Use case
Build display labels.
$concat: practical example
{ $project: { fullName: { $concat: ["$firstName", " ", "$lastName"] } } }💡 Explanation
Concatenates strings; null inputs can yield null, so use
$ifNull when needed.
When to use it
Build display labels.Key Takeaways
- Concatenates strings; null inputs can yield null, so use
$ifNullwhen needed. - Typical use: Build display labels.