fix(guide): simplify directory structure

guide/english/sql/sql-not-operator/index.md

@@ -0,0 +1,17 @@
+---
+title: SQL not Operator
+---
+## SQL not Operator
+
+You can use the `NOT` operator in the `WHERE` clause of `SELECT` statement. You use it when you want to select a condition that is not true.
+
+Here is an example that selects all persons that are not male:
+
+```sql
+SELECT Id, Name, DateOfBirth, Gender
+FROM Person
+WHERE NOT Gender = "M"
+```
+
+
+