The SORT statement will force a sort of the array of already produced intermediate results in the current block. SORT allows specifying one or multiple sort criteria and directions. The general syntax is:
SORT expression direction
Example query that is sorting by lastName (in ascending order), then firstName (in ascending order), then by id (in descending order):
FOR u IN users SORT u.lastName, u.firstName, u.id DESC RETURN u
Specifying the direction is optional. The default (implicit) direction for a sort expression is the ascending order. To explicitly specify the sort direction, the keywords ASC (ascending) and DESC can be used. Multiple sort criteria can be separated using commas. In this case the direction is specified for each expression sperately. For example
SORT doc.lastName, doc.firstName
will first sort documents by lastName in ascending order and then by firstName in ascending order.
SORT doc.lastName DESC, doc.firstName
will first sort documents by lastName in descending order and then by firstName in ascending order.
SORT doc.lastName, doc.firstName DESC
will first sort documents by lastName in ascending order and then by firstName in descending order.
Note: when iterating over collection-based arrays, the order of documents is always undefined unless an explicit sort order is defined using SORT.
Note that constant SORT expressions can be used to indicate that no particular sort order is desired. Constant SORT expressions will be optimized away by the AQL optimizer during optimization, but specifying them explicitly may enable further optimizations if the optimizer does not need to take into account any particular sort order. This is especially the case after a COLLECT statement, which is supposed to produce a sorted result. Specifying an extra SORT null after the COLLECT statement allows to AQL optimizer to remove the post-sorting of the collect results altogether.