Add Create Table Adds A Data Type as a postgres til

README.md

@@ -7,7 +7,7 @@ variety of languages and technologies. These are things that don't really
 warrant a full blog post. These are mostly things I learn by pairing with
 smart people at [Hashrocket](http://hashrocket.com/).
 
-_401 TILs and counting..._
+_402 TILs and counting..._
 
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@@ -180,6 +180,7 @@ _401 TILs and counting..._
 - [Count Records By Type](postgres/count-records-by-type.md)
 - [Create A Composite Primary Key](postgres/create-a-composite-primary-key.md)
 - [Create hstore From Two Arrays](postgres/create-hstore-from-two-arrays.md)
+- [Create Table Adds A Data Type](postgres/create-table-adds-a-data-type.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)

postgres/create-table-adds-a-data-type.md

@@ -0,0 +1,32 @@
+# Create Table Adds A Data Type
+
+Each time you create a table in PostgreSQL, a new data type represented by
+that table is created and added to the `pg_type` table. According to the
+Postgres docs:
+
+> CREATE TABLE also automatically creates a data type that represents the
+> composite type corresponding to one row of the table. Therefore, tables
+> cannot have the same name as any existing data type in the same schema.
+
+For instance, if you create a `users` table like so:
+
+```sql
+create table users (
+  id serial primary key,
+  first_name varchar not null,
+  last_name varchar not null
+);
+```
+
+then the `pg_type` will now contain an entry with a `typname` of `users`.
+
+```sql
+select * from pg_type where typname = 'users';
+-[ RECORD 1 ]--+------------
+typname        | users
+typnamespace   | 2200
+typowner       | 16384
+...
+```
+
+h/t Bruce Momjian