diff --git a/README.md b/README.md
index 982e399..c089bc2 100644
--- a/README.md
+++ b/README.md
@@ -735,3 +735,7 @@ The following guidelines indicate when the use of an index should be reconsidere
 ### Change DATA TYPE
 
     ALTER TABLE table_name MODIFY COLUMN column_name datatype;
+
+### NOT NULL
+
+