Add documentation for IN [...] and add links.

Change-Id: Ifdab278567e8e89d5c8f7a1916fdd8f9131808f3
Reviewed-on: https://asterix-gerrit.ics.uci.edu/1254
Sonar-Qube: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Till Westmann <tillw@apache.org>
diff --git a/asterixdb/asterix-doc/src/main/markdown/sqlpp/1_intro.md b/asterixdb/asterix-doc/src/main/markdown/sqlpp/1_intro.md
index fdc04cb..f7df33f 100644
--- a/asterixdb/asterix-doc/src/main/markdown/sqlpp/1_intro.md
+++ b/asterixdb/asterix-doc/src/main/markdown/sqlpp/1_intro.md
@@ -27,11 +27,11 @@
 relational databases, while SQL++ is much newer and targets the nested, schema-optional
 (or even schema-less) world of modern NoSQL systems.
 
-In the context of Apache AsterixDB, SQL++ is intended for working with the Asterix Data Model (ADM),
-a data model based on a superset of JSON with an enriched and flexible type system.
+In the context of Apache AsterixDB, SQL++ is intended for working with the Asterix Data Model
+([ADM](../datamodel.html)),a data model based on a superset of JSON with an enriched and flexible type system.
 New AsterixDB users are encouraged to read and work through the (much friendlier) guide
-"AsterixDB 101: An ADM and SQL++ Primer" before attempting to make use of this document.
-In addition, readers are advised to read through the Asterix Data Model (ADM) reference guide
+"[AsterixDB 101: An ADM and SQL++ Primer](primer-sqlpp.html)" before attempting to make use of this document.
+In addition, readers are advised to read through the [Asterix Data Model (ADM) reference guide](../datamodel.html)
 first as well, as an understanding of the data model is a prerequisite to understanding SQL++.
 
 In what follows, we detail the features of the SQL++ language in a grammar-guided manner.
diff --git a/asterixdb/asterix-doc/src/main/markdown/sqlpp/3_query.md b/asterixdb/asterix-doc/src/main/markdown/sqlpp/3_query.md
index bfe4f0e..68573e2 100644
--- a/asterixdb/asterix-doc/src/main/markdown/sqlpp/3_query.md
+++ b/asterixdb/asterix-doc/src/main/markdown/sqlpp/3_query.md
@@ -874,14 +874,15 @@
 within a query the subquery occurs -- and again, its result is never automatically cast into a scalar.
 
 ## <a id="Vs_SQL-92">SQL++ vs. SQL-92</a>
-The following matrix is a quick "key differences cheat sheet" for SQL++ and SQL-92.
+The following matrix is a quick "SQL-92 compatibility cheat sheet" for SQL++.
 
 | Feature |  SQL++ | SQL-92 |
 |----------|--------|--------|
 | SELECT * | Returns nested records | Returns flattened concatenated records |
 | Subquery | Returns a collection  | The returned collection is cast into a scalar value if the subquery appears in a SELECT list or on one side of a comparison or as input to a function |
-| LEFT OUTER JOIN |  Fills in `MISSING` for non-matches  |   Fills in `NULL`(s) for non-matches    |
-| UNION ALL       | Allows heterogenous inputs and output | Input streams must be UNION-compatible and output field names are drawn from the first input stream
+| LEFT OUTER JOIN |  Fills in `MISSING`(s) for non-matches  |   Fills in `NULL`(s) for non-matches    |
+| UNION ALL       | Allows heterogeneous inputs and output | Input streams must be UNION-compatible and output field names are drawn from the first input stream
+| IN constant_expr | The constant expression has to be an array or multiset, i.e., [..,..,...] | The constant collection can be represented as comma-separated items in a paren pair |
 | String literal | Double quotes or single quotes | Single quotes only |
 | Delimited identifiers | Backticks | Double quotes |
 
diff --git a/asterixdb/asterix-doc/src/site/markdown/aql/datamodel.md b/asterixdb/asterix-doc/src/site/markdown/datamodel.md
similarity index 100%
rename from asterixdb/asterix-doc/src/site/markdown/aql/datamodel.md
rename to asterixdb/asterix-doc/src/site/markdown/datamodel.md
diff --git a/asterixdb/asterix-doc/src/site/site.xml b/asterixdb/asterix-doc/src/site/site.xml
index 33ce7eb..4c0ba6e 100644
--- a/asterixdb/asterix-doc/src/site/site.xml
+++ b/asterixdb/asterix-doc/src/site/site.xml
@@ -85,7 +85,7 @@
     </menu>
 
     <menu name="Data Model">
-      <item name="The Asterix Data Model" href="aql/datamodel.html"/>
+      <item name="The Asterix Data Model" href="datamodel.html"/>
     </menu>
 
     <menu name="Queries - SQL++">
@@ -108,7 +108,6 @@
 
     <menu name="API/SDK">
       <item name="HTTP API" href="api.html"/>
-      <item name="Javascript SDK" href="aql/js-sdk.html"/>
     </menu>
 
     <menu ref="reports"/>