1) What is left join? 2) What is self join? 3) Difference between truncate and delete 4) What is polymorphism? 5) What is ORM?

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1) Left join combines rows from two tables based on a related column, including all rows from the left table. 2) Self join is when a table is joined with itself. 3) Truncate removes all rows from a table, while delete removes specific rows. 4) Polymorphism allows objects to be treated as instances of their parent class. 5) ORM is Object-Relational Mapping, a programming technique for converting data between incompatible type systems.

Left join combines rows from two tables based on a related column, including all rows from the left table. Example: SELECT * FROM table1 LEFT JOIN table2 ON table1.id = table2.id
Self join is when a table is joined with itself. Example: SELECT * FROM employees e1, employees e2 WHERE e1.manager_id = e2.employee_id
Truncate removes all rows from a table, while delete removes specific rows. Truncate is faster but cannot be rolled back. Example: TRUNCATE TABLE table_name
Polymorphism allows objects to be treated as instances of their parent class. Example: Animal class with Dog and Cat subclasses can be treated as Animal objects.
ORM is Object-Relational Mapping, a programming technique for converting data between incompatible type systems. Example: Using Hibernate in Java to map Java objects to database tables.

1) What is left join? 2) What is self join? 3) Difference between truncate and delete 4) What is polymorphism? 5) What is ORM?

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