Fix AQL doc for SQL fans.
Change-Id: I36b94af0280909ba49eca4ad311db3a633b305b9
Reviewed-on: https://asterix-gerrit.ics.uci.edu/420
Tested-by: Ian Maxon <imaxon@apache.org>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Till Westmann <tillw@apache.org>
diff --git a/asterix-doc/src/site/markdown/aql/primer-sql-like.md b/asterix-doc/src/site/markdown/aql/primer-sql-like.md
index 1d560e2..0debb94 100644
--- a/asterix-doc/src/site/markdown/aql/primer-sql-like.md
+++ b/asterix-doc/src/site/markdown/aql/primer-sql-like.md
@@ -353,7 +353,7 @@
naming five of the most frequently used clauses from the syntax of a full AQL query.
AQL also includes _group by_ and _limit_ clauses, as you will see shortly.
Roughly speaking, for SQL afficiandos, the _for_ clause in AQL is like the _from_ clause in SQL,
-the _return_ clause in AQL is like the _return_ clause in SQL (but appears at the end instead of
+the _return_ clause in AQL is like the _select_ clause in SQL (but appears at the end instead of
the beginning of a query), the _let_ clause in AQL is like SQL's _with_ clause, and the _where_
and _order by_ clauses in both languages are similar.
@@ -374,10 +374,10 @@
where $user.id = 8
select $user;
-The query's _for_ clause binds the variable `$user` incrementally to the data instances residing in
+The query's _from_ clause binds the variable `$user` incrementally to the data instances residing in
the dataset named FacebookUsers.
Its _where_ clause selects only those bindings having a user id of interest, filtering out the rest.
-The _return_ clause returns the (entire) data instance for each binding that satisfies the predicate.
+The _select_ clause returns the (entire) data instance for each binding that satisfies the predicate.
Since this dataset is indexed on user id (its primary key), this query will be done via a quick index lookup.
The expected result for our sample data is as follows:
@@ -510,7 +510,7 @@
{ "uname": "SuzannaTillson", "message": " like iphone the voicemail-service is awesome" }
-(It is worth knowing, with respect to influencing AsterixDB's query evaluation, that nested _for_
+(It is worth knowing, with respect to influencing AsterixDB's query evaluation, that nested _from_
clauses---a.k.a. joins--- are currently evaluated with the "outer" clause probing the data of the "inner"
clause.)
@@ -707,14 +707,14 @@
"count": count($t)
};
-The _for_ clause incrementally binds $t to tweets, and the _group by_ clause groups the tweets by its
+The _from_ clause incrementally binds $t to tweets, and the _group by_ clause groups the tweets by its
issuer's Twitter screen-name.
Unlike SQL, where data is tabular---flat---the data model underlying AQL allows for nesting.
-Thus, following the _group by_ clause, the _return_ clause in this query sees a sequence of $t groups,
+Thus, following the _group by_ clause, the _select_ clause in this query sees a sequence of $t groups,
with each such group having an associated $uid variable value (i.e., the tweeting user's screen name).
-In the context of the return clause, due to "... with $t ...", $uid is bound to the tweeter's id and $t
+In the context of the _select_ clause, due to "... keeping $t ...", $uid is bound to the tweeter's id and $t
is bound to the _set_ of tweets issued by that tweeter.
-The return clause constructs a result record containing the tweeter's user id and the count of the items
+The _select_ clause constructs a result record containing the tweeter's user id and the count of the items
in the associated tweet set.
The query result will contain one such record per screen name.
This query also illustrates another feature of AQL; notice that each user's screen name is accessed via a
@@ -769,7 +769,7 @@
from $t in dataset TweetMessages
group by $uid := $t.user.screen-name keeping $t
- let $c := count($t)
+ with $c := count($t)
order by $c desc
limit 3
select {