diff --git a/10.Key_Constraint_types b/10.Key_Constraint_types.sql
similarity index 99%
rename from 10.Key_Constraint_types
rename to 10.Key_Constraint_types.sql
index 2001ac4..527014c 100644
--- a/10.Key_Constraint_types
+++ b/10.Key_Constraint_types.sql
@@ -76,6 +76,7 @@ The email column can have one or more NULL values, but each non-NULL email must
 ---
 
  3. NOT NULL Constraint Failure
+    ============================
 
 The NOT NULL constraint ensures that a column cannot contain NULL values. If you try to insert a NULL value into a NOT NULL column, the operation will fail.
 
diff --git a/13.superkey_candidate_key b/13.superkey_candidate_key.sql
similarity index 100%
rename from 13.superkey_candidate_key
rename to 13.superkey_candidate_key.sql
diff --git a/14.1.case_when b/14.1.case_when_.sql
similarity index 100%
rename from 14.1.case_when
rename to 14.1.case_when_.sql
diff --git a/14.Aggregation , NOT IN , AND , OR , IN , ALAIS b/14.Aggregation , NOT IN , AND , OR , IN , ALAIS.sql
similarity index 100%
rename from 14.Aggregation , NOT IN , AND , OR , IN , ALAIS
rename to 14.Aggregation , NOT IN , AND , OR , IN , ALAIS.sql
diff --git a/15.null handling b/15.null handling.sql
similarity index 100%
rename from 15.null handling
rename to 15.null handling.sql
diff --git a/16.String Handling b/16.String Handling.sql
similarity index 100%
rename from 16.String Handling
rename to 16.String Handling.sql
diff --git a/17.Subquery b/17.Subquery.sql
similarity index 100%
rename from 17.Subquery
rename to 17.Subquery.sql
diff --git a/18.views b/18.views.sql
similarity index 100%
rename from 18.views
rename to 18.views.sql
diff --git a/20.Window Function b/20.Window Function.sql
similarity index 100%
rename from 20.Window Function
rename to 20.Window Function.sql
diff --git a/20.joins b/20.joins.sql
similarity index 100%
rename from 20.joins
rename to 20.joins.sql
diff --git a/21.union_union_all b/21.union_union_all.sql
similarity index 100%
rename from 21.union_union_all
rename to 21.union_union_all.sql
diff --git a/22.index_explain b/22.index_explain.sql
similarity index 100%
rename from 22.index_explain
rename to 22.index_explain.sql
diff --git a/23.partition b/23.partition.sql
similarity index 100%
rename from 23.partition
rename to 23.partition.sql
diff --git a/6.SQL Basic Commands CRUD Create, Read, Update, and Delete b/6.SQL Basic Commands CRUD Create, Read, Update, and Delete.sql
similarity index 99%
rename from 6.SQL Basic Commands CRUD Create, Read, Update, and Delete
rename to 6.SQL Basic Commands CRUD Create, Read, Update, and Delete.sql
index 8b0c5c1..3edda75 100644
--- a/6.SQL Basic Commands CRUD Create, Read, Update, and Delete	
+++ b/6.SQL Basic Commands CRUD Create, Read, Update, and Delete.sql	
@@ -1,4 +1,4 @@
-
+✅ Done 
 My complete SQL Masterclass Notes in Tanglish is now live! Covers 30+ topics with syntax, examples, and step-by-step explanations. 
 Perfect for both beginners and professionals to master SQL easily. Check it out here 👉 https://topmate.io/dataengineering/1697791
 
diff --git a/7.types_of_create_table b/7.types_of_create_table.sql
similarity index 96%
rename from 7.types_of_create_table
rename to 7.types_of_create_table.sql
index d78b9ee..5dd3d0c 100644
--- a/7.types_of_create_table
+++ b/7.types_of_create_table.sql
@@ -1,9 +1,9 @@
+ ✅ Done 
 My complete SQL Masterclass Notes in Tanglish is now live! Covers 30+ topics with syntax, examples, and step-by-step explanations. 
 Perfect for both beginners and professionals to master SQL easily. Check it out here 👉 https://topmate.io/dataengineering/1697791
 
 ====================================================================================
 
-
 -- 1) Basic create
 CREATE TABLE employees (
     employee_id INT PRIMARY KEY,
@@ -20,7 +20,7 @@ CREATE TABLE departments (
     location  VARCHAR(100) NOT NULL
 );
 
--- 3) Create table as select
+-- 3) Create table as select ---(CTAS)
 CREATE TABLE high_paid_employees AS
 SELECT 
     employee_id, 
diff --git a/8.alter b/8.alter.sql
similarity index 100%
rename from 8.alter
rename to 8.alter.sql
diff --git a/9.where b/9.where.sql
similarity index 99%
rename from 9.where
rename to 9.where.sql
index 237a30b..82d8fa9 100644
--- a/9.where
+++ b/9.where.sql
@@ -1,3 +1,4 @@
+✅ Done 
 My complete SQL Masterclass Notes in Tanglish is now live! Covers 30+ topics with syntax, examples, and step-by-step explanations. 
 Perfect for both beginners and professionals to master SQL easily. Check it out here 👉 https://topmate.io/dataengineering/1697791