Format, Parameters

GROUP BY divides the rows in the data stream into multiple groups, for each group keeps one row of data and discard the rest rows; it is always followed by an aggregation operation that generates an aggregated value for each group.

Syntax:

• Format: group by <column1> as <alias1>, <column2> as <alias2>, ...
• Parameters: see table below
• Affected columns：<column> and all its homologous columns

Analysis

n(as n1).re().n(as n2) as path
group by n1.shape, n2.color
return path, count(path)

In the UQL statement above, Group By groups the one-step paths resulted from a template query; it groups results based on initial nodes' shapes, then based on colours of terminal nodes; then return results after counting the number of paths in each group.

ATTR

Example: Group all cards by card level, return the total number of cards at each level

find().nodes({@card}) as n
group by n.level as level
return level, count(n)

NODE

Example: find cards held by Customer CU001, CU002, CU003, and return the array of Card IDs and their owners

n({_id in ["CU001","CU002","CU003"]} as n1)
  .re({@has}).n({@card} as n2)
group by n1
return n1{*}, collect(n2._id)

Multi-level Grouping

Example: find all-level customers'ownership of all-level cards, return customer levels, card levels, and the number of cards owned by each customer

n({@customer} as n1)
  .re({@has}).n({@card} as n2)
group by n1.level as a, n2.level as b
return table(a, b, count(n2))