Fix alter table query (#5137)

* Update 101-alter-table.md

Previously :
     ALTER TABLE tableName
     ALTER COLUMN columnName TYPE newDataType;
results in syntax error

Now:
     ALTER TABLE tableName
     MODIFY COLUMN columnName newDataType;

* Update 101-alter-table.md

Added how to drop an primary key

* Update src/data/roadmaps/sql/content/102-ddl/101-alter-table.md

Co-authored-by: dsh <daniel.s.holdsworth@gmail.com>

---------

Co-authored-by: Kamran Ahmed <kamranahmed.se@gmail.com>
Co-authored-by: dsh <daniel.s.holdsworth@gmail.com>

src/data/roadmaps/sql/content/102-ddl/101-alter-table.md

@@ -46,7 +46,7 @@ To modify the datatype of a column:
 
 ```sql
 ALTER TABLE tableName
-ALTER COLUMN columnName TYPE newDataType;
+MODIFY COLUMN columnName newDataType;
 ```
 
 ## Add/Drop Constraints
@@ -66,4 +66,10 @@ ALTER TABLE tableName
 DROP CONSTRAINT constraintName;
 ```
 
+To drop PRIMARY KEY:
+
+```sql
+ALTER TABLE table_name
+DROP PRIMARY KEY;
+
 In conclusion, `ALTER TABLE` in SQL lets you alter the structure of an existing table. This is a powerful command that lets you dynamically add, modify, and delete columns as well as the constraints placed on them. It ensures you are more flexible in dealing with changing data storage requirements.