Add Day Of Week For A Date as a postgres til

README.md

@@ -136,6 +136,7 @@ _310 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)
+- [Day Of Week For A Date](postgres/day-of-week-for-a-date.md)
 - [Default Schema](postgres/default-schema.md)
 - [Defining Arrays](postgres/defining-arrays.md)
 - [Edit Existing Functions](postgres/edit-existing-functions.md)

postgres/day-of-week-for-a-date.md

@@ -0,0 +1,22 @@
+# Day Of Week For A Date
+
+Given a `date` in PostgreSQL
+
+```sql
+> select '2050-1-1'::date;
+    date
+------------
+ 2050-01-01
+```
+
+you can determine the day of the week for that date with the `date_part()`
+function
+
+```sql
+> select date_part('dow', '2050-1-1'::date);
+ date_part
+-----------
+         6
+```
+
+[source](http://www.postgresql.org/docs/current/static/functions-datetime.html)