Add Count Records By Type as a postgres til.

README.md

@@ -52,6 +52,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 
 ### postgres
 
+- [Count Records By Type](postgres/count-records-by-type.md)
 - [Extracting Nested JSON Data](postgres/extracting-nested-json-data.md)
 - [Timestamp Functions](postgres/timestamp-functions.md)
 - [Toggling The Pager In PSQL](postgres/toggling-the-pager-in-psql.md)

postgres/count-records-by-type.md

@@ -0,0 +1,17 @@
+# Count Records By Type
+
+If you have a table with some sort of type column on it, you can come up
+with a count of the records in that table by type. You just need to take
+advantage of `group by`:
+
+```sql
+> select type, count(*) from pokemon group by type;
+
+  type   | count 
+-----------------
+ fire    |    10
+ water   |     4
+ plant   |     7
+ psychic |     3
+ rock    |    12
+```