Database Reference
In-Depth Information
Reversing clustering order at query time
Using our existing
user_status_updates
table, we can instruct Cassandra to return
results in reverse order of
id
:
SELECT "id", DATEOF("id"), "body"
FROM "user_status_updates"
WHERE "username" = 'alice'
ORDER BY "id" DESC;
This is the first time we've seen an
ORDER BY
in CQL, but it should be familiar to anyone
who's worked with a SQL database: the
DESC
tells Cassandra that we want to order rows
by descending values in the
id
column:
You might assume that the
ORDER BY
gives us a lot of flexibility in ordering rows—you
might think that
id
can just as well be replaced by any other column. Let's see for
ourselves:
SELECT "id", DATEOF("id"), "body"
FROM "user_status_updates"
WHERE "username" = 'alice'
ORDER BY "body" DESC;
Here, we're trying to sort our rows by descending (Z-A) values in the
body
field. Alas, it is
not to be:
