Add Getting A Slice Of An Array as a postgres til.

postgres/getting-a-slice-of-an-array.md

@@ -0,0 +1,25 @@
+# Getting A Slice Of An Array
+
+Postgres has a very natural syntax for grabbing a slice of an array. You
+simply add brackets after the array declaring the lower and upper bounds
+of the slice separated by a colon.
+
+```sql
+> select (array[4,5,6,7,8,9])[2:4];
+  array
+---------
+ {5,6,7}
+```
+
+Notice that the bounds are inclusive, the array index is `1`-based, and the
+array declaration above needs to be wrapped in parentheses in order to not
+trip up the array slice syntax.
+
+You can also select rectangular slices from two dimensional arrays like so:
+
+```sql
+> select (array[[1,2,3],[4,5,6],[7,8,9]])[2:3][1:2];
+     array
+---------------
+ {{4,5},{7,8}}
+```