SQL

Practice 32 SQL interview questions with detailed answers. Part of the Sql track on Java Interview Hub.

• What is SQL?
• Where do we use SQL?
• What are the SQL Statements?
• What is a join?
• What is the purpose of the SELECT statement in MySQL?
• What is Normalization?
• What is the different datatype in MySQL?
• What is the difference between a primary key and a unique key?
• Foreign key constraint?
• The difference between NULL and zero in MySQL is that:
• What is a Database transaction?
• Difference between INNER JOIN and NATURAL JOIN:
• How do you perform a self-join in MYSQL?
• What is a trigger, and how do you create one in MySQL?
• What is the stored procedure, and how do you create one in MySQL?
• What is a cursor, and how do you use one in MySQL?
• What is a user-defined function, and how do you create one in MySQL?
• What are aggregate functions in SQL?
• What is the difference between WHERE and HAVING clause ?
• What are indexes in SQL ?
• How can you identify which indexes are being used in a query?
• Can you have an index on a view? If yes, how?
• You have two tables, shop_1 and shop_2, both having the same structure with customer_id and customer_name. Write a query that retrieves the names of customers who appear in both tables.
• Difference between INNER JOIN and OUTER JOIN?
• Difference Between WHERE and HAVING
• Difference Between UNION and UNION ALL?
• Difference Between DELETE and TRUNCATE
• Difference Between PRIMARY KEY and UNIQUE
• Difference Between DROP and TRUNCATE?
• Difference Between VARCHAR and CHAR?
• Difference Between IN and EXISTS
• Difference Between JOIN and SUBQUERY?