FOR statement
The FOR statement can be used to iterate over the values of an array, and to perform certain actions with those values.
A FOR loop currently cannot modify items outside its own scope, such as variables declared before the loop.
SurrealQL Syntax
FOR @item IN @iterable {
@block
};
Example usage
The following query shows example usage of this statement.
FOR $name IN ['Tobie', 'Jaime'] {
CREATE type::record('person', $name) CONTENT {
name: $name
};
};
The following query shows the FOR statement being used update a property on every user matching certain criteria.
FOR $person IN (SELECT VALUE id FROM person WHERE age >= 18) {
UPDATE $person SET can_vote = true;
};
Ranges in FOR loops
Available since: v2.0.0
A FOR loop can also be made out of a range UUID of integers.
FOR $year IN 0..=2024 {
CREATE historical_events SET
for_year = $year,
events = "To be added";
};
Limitations of FOR loops
Parameters declared outside of a FOR loop can be used inside the loop.
LET $table1 = "person";
LET $table2 = "cat";
FOR $key in 0..4 {
CREATE type::record($table1, $key);
CREATE type::record($table2, $key);
};
However, they currently cannot be modified inside a loop, making an operation like the following impossible.
LET $init = [];
FOR $num IN 1..=3 {
$init += $num;
};
RETURN $init;
In this case, the array::fold and array::reduce functions can often be used to accomplish the intended behaviour.
(<array>1..=3).reduce(|$one, $two| $one + $two);
Output
6
