Posidex Technologies SQL Developer Interview Questions and Answers

Join is used to combine rows from two or more tables based on a related column between them.

• Join is used to retrieve data from multiple tables.

• Syntax: SELECT column_name(s) FROM table1 JOIN table2 ON table1.column_name = table2.column_name;

• Types of joins: INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL OUTER JOIN, CROSS JOIN.

• Example: SELECT customers.name, orders.order_date FROM customers JOIN orders ON customers.customer_id =

Constrain is a rule that restricts the values in a database column. DDL is a set of SQL commands used to create, modify, and delete database objects.

• Constrains ensure data integrity and prevent invalid data from being inserted into a database.

• DDL includes commands like CREATE, ALTER, and DROP to manage database objects like tables, indexes, and views.

• Constrains are defined using DDL commands like CHECK, UNIQUE, and FOR...read more