Add Set Inclusion With hstore as a postgres til.

README.md

@@ -142,6 +142,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 - [Max Identifier Length Is 63 Bytes](postgres/max-identifier-length-is-63-bytes.md)
 - [Restart A Sequence](postgres/restart-a-sequence.md)
 - [Send A Command To psql](postgres/send-a-command-to-psql.md)
+- [Set Inclusion With hstore](postgres/set-inclusion-with-hstore.md)
 - [Special Math Operators](postgres/special-math-operators.md)
 - [String Contains Another String](postgres/string-contains-another-string.md)
 - [Temporarily Disable Triggers](postgres/temporarily-disable-triggers.md)

postgres/set-inclusion-with-hstore.md

@@ -0,0 +1,22 @@
+# Set Inclusion With hstore
+
+In PostgreSQL, `hstore` records can be compared via set inclusion. The `@>`
+and `<@` operators can be used for this. The `@>` operator checks if the
+right operand is a subset of the left operand. The `<@` operator checks if
+the left operand is a subset of the right operand.
+
+```sql
+> select '"one"=>"1", "two"=>"2", "three"=>"3"'::hstore @> '"two"=>"2"'::hstore;
+ ?column?
+ ----------
+  t
+
+> select '"one"=>"1", "two"=>"2", "three"=>"3"'::hstore <@ '"two"=>"2"'::hstore;
+ ?column?
+----------
+ f
+```
+
+See the [`hstore` PostgreSQL
+docs](http://www.postgresql.org/docs/current/static/hstore.html) for more
+details.