Add Creating Custom Types as a postgres til

Author: jbranchaud

README.md

@@ -179,6 +179,7 @@ _393 TILs and counting..._
 - [Create A Composite Primary Key](postgres/create-a-composite-primary-key.md)
 - [Create hstore From Two Arrays](postgres/create-hstore-from-two-arrays.md)
 - [Creating Conditional Constraints](postgres/creating-conditional-constraints.md)
+- [Creating Custom Types](postgres/creating-custom-types.md)
 - [Day Of Week By Name For A Date](postgres/day-of-week-by-name-for-a-date.md)
 - [Day Of Week For A Date](postgres/day-of-week-for-a-date.md)
 - [Default Schema](postgres/default-schema.md)

postgres/creating-custom-types.md

@@ -0,0 +1,32 @@
+# Creating Custom Types
+
+PostgreSQL has support for creating custom types. When you need something
+more expressive than the built-in types and you don't want your data spread
+across multiple columns, you can instead create a custom type.
+
+```sql
+create type dimensions as (
+  width integer,
+  height integer,
+  depth integer
+);
+```
+
+This new type can then be used in the definition of a new table
+
+```sql
+create table moving_boxes (
+  id serial primary key,
+  dims dimensions not null
+);
+```
+
+and when inserting data
+
+```sql
+insert into moving_boxes (dims) values (row(3,4,5)::dimensions);
+```
+
+See the [`create type`
+docs](http://www.postgresql.org/docs/current/static/sql-createtype.html) for
+more details.