collect()¶

The collect() function returns a list containing the values returned by an expression. Using this function aggregates data by merging multiple records or values into a single list.

The aggregate function collect() works like GROUP BY in SQL.

Examples¶

nebula> UNWIND [1, 2, 1] AS a \
        RETURN a;
+---+
| a |
+---+
| 1 |
+---+
| 2 |
+---+
| 1 |
+---+

nebula> UNWIND [1, 2, 1] AS a \
        RETURN collect(a);
+------------+
| collect(a) |
+------------+
| [1, 2, 1]  |
+------------+

nebula> UNWIND [1, 2, 1] AS a \
        RETURN a, collect(a), size(collect(a));
+---+------------+------------------+
| a | collect(a) | size(COLLECT(a)) |
+---+------------+------------------+
| 2 | [2]        | 1                |
+---+------------+------------------+
| 1 | [1, 1]     | 2                |
+---+------------+------------------+

# The following examples sort the results in descending order, limit output rows to 3, and collect the output into a list.œ
nebula> UNWIND ["c", "b", "a", "d" ] AS p \
        WITH p AS q \
        ORDER BY q DESC LIMIT 3 \
        RETURN collect(q);
+-----------------+
| collect(q)      |
+-----------------+
| ["d", "c", "b"] |
+-----------------+

nebula> WITH [1, 1, 2, 2] AS coll \
        UNWIND coll AS x \
        WITH DISTINCT x \
        RETURN collect(x) AS ss;
+--------+
| ss     |
+--------+
| [1, 2] |
+--------+

nebula> MATCH (n:player) \
        RETURN collect(n.age);
+---------------------------------------------------------------+
| collect(n.age)                                                |
----------------------------------------------------------------+
| [32, 32, 34, 29, 41, 40, 33, 25, 40, 37, ...
...

# The following example aggregates all the players' names by their ages.
nebula> MATCH (n:player) \
        RETURN n.age AS age, collect(n.name);
+-----+--------------------------------------------------------------------------+
| age | collect(n.name)                                                          |
+-----+--------------------------------------------------------------------------+
| 24  | ["Giannis Antetokounmpo"]                                                |
+-----+--------------------------------------------------------------------------+
| 20  | ["Luka Doncic"]                                                          |
+-----+--------------------------------------------------------------------------+
| 25  | ["Joel Embiid", "Kyle Anderson"]                                         |
+-----+--------------------------------------------------------------------------+
...

Last update: July 19, 2021