Databases Reference
In-Depth Information
As we've seen in the previous queries, the simplest thing we can do is return the plays
we've found:
RETURN DISTINCT
play.title
AS
play
DISTINCT
ensures we return unique results. Because each play can be performed mul‐
tiple times in the same theater, sometimes in different productions, we can end up with
duplicate play titles.
DISTINCT
filters these out.
We can enrich this result in several ways, including aggregating, ordering, filtering, and
limiting the returned data. For example, if we're only interested in the
number
of plays
that match our criteria, we apply the
count
function:
RETURN
count
(play)
If we want to rank the plays by the number of performances, we'll need first to bind the
PERFORMANCE_OF
relationship in the
MATCH
clause to an identifier, called
p
, which we can
then
count
and order:
START
theater=
node
:venue(name=
'Theatre Royal'
),
newcastle=
node
:city(name=
'Newcastle'
),
bard=
node
:author(lastname=
'Shakespeare'
)
MATCH
(newcastle)<-[:STREET|CITY*1..2]-(theater)
<-[:VENUE]-()-[p:PERFORMANCE_OF]->()-[:PRODUCTION_OF]->
(play)<-[:WROTE_PLAY]-(bard)
RETURN
play.title
AS
play,
count
(p)
AS
performance_count
ORDER BY
performance_count
DESC
The
RETURN
clause here counts the number of
PERFORMANCE_OF
relationships using the
identifier
p
(which is bound to the
PERFORMANCE_OF
relationships in the
MATCH
clause)
and aliases the result as
performance_count
. It then orders the results based on
per
formance_count
, with the most frequently performed play listed first:
+-------------------------------------+
| play | performance_count |
+-------------------------------------+
| "Julius Caesar" | 2 |
| "The Tempest" | 1 |
+-------------------------------------+
2 rows
Query Chaining
Before we leave our brief tour of Cypher, there is one more feature that it is useful to
know about—the
WITH
clause. Sometimes it's just not practical (or possible) to do
everything you want in a single
MATCH
. The
WITH
clause allows us to chain together several
matches, with the results of the previous query part being piped into the next. In the
following example we find the plays written by Shakespeare, and order them based on
