Add Shorthand Absolute Value Operator as a postgres til

README.md

@@ -9,7 +9,7 @@ and pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://tinyletter.com/jbranchaud).
 
-_936 TILs and counting..._
+_937 TILs and counting..._
 
 ---
 
@@ -512,6 +512,7 @@ _936 TILs and counting..._
 - [Set Inclusion With hstore](postgres/set-inclusion-with-hstore.md)
 - [Set A Seed For The Random Number Generator](postgres/set-a-seed-for-the-random-number-generator.md)
 - [Sets With The Values Command](postgres/sets-with-the-values-command.md)
+- [Shorthand Absolute Value Operator](postgres/shorthand-absolute-value-operator.md)
 - [Show All Versions Of An Operator](postgres/show-all-versions-of-an-operator.md)
 - [Sleeping](postgres/sleeping.md)
 - [Special Math Operators](postgres/special-math-operators.md)

postgres/shorthand-absolute-value-operator.md

@@ -0,0 +1,24 @@
+# Shorthand Absolute Value Operator
+
+Postgres offers many [math
+functions](https://www.postgresql.org/docs/8.0/functions-math.html) including
+`abs` for computing the absolute value of a number.
+
+```sql
+> select abs(-1);
+ abs
+-----
+   1
+(1 row)
+```
+
+There is also an absolute value _operator_ -- the `@` symbol. This can be used
+to do the same thing.
+
+```sql
+> select @ -1;
+ ?column?
+----------
+        1
+(1 row)
+```