Crake a MySql interview questions and answers of part 1

 Dear All,

1.What is a foreign key in MySQL?

A foreign key is a column or set of columns in a table that is used to establish a link between two tables. It is a reference to a primary key in another table and is used to maintain data integrity.

2. What is the difference between CHAR and VARCHAR in MySQL?

CHAR is a fixed-length string type that is always the same size, while VARCHAR is a variable-length string type that can be up to a specified maximum size.

3. What is the use of the GROUP BY clause in MySQL?

The GROUP BY clause is used to group rows based on one or more columns in a table. It is often used with aggregate functions like COUNT, SUM, and AVG to generate summary reports.

4.What is a stored procedure in MySQL?

A stored procedure is a set of SQL statements that are stored in the database and can be called by name from a client application. It is used to encapsulate complex logic and improve performance by reducing network traffic.

5. What is the difference between DELETE and TRUNCATE in MySQL?

DELETE is a DML (Data Manipulation Language) statement that removes rows from a table based on a specified condition. TRUNCATE is a DDL (Data Definition Language) statement that removes all rows from a table and resets the auto-increment counter.

6. What is the use of the JOIN clause in MySQL?

The JOIN clause is used to combine rows from two or more tables based on a related column. It is often used to retrieve data from multiple tables in a single query.

7. What is the use of the ORDER BY clause in MySQL?

The ORDER BY clause is used to sort the rows in a result set based on one or more columns in ascending or descending order.

8. What is the difference between UNION and UNION ALL in MySQL?

UNION combines the result sets of two or more SELECT statements into a single result set, removing any duplicates. UNION ALL does the same thing, but does not remove duplicates.

9. What is the use of the IN operator in MySQL?

The IN operator is used to specify a list of values to be matched in a WHERE clause. It is often used with the NOT operator to exclude certain values from a result set.

10. What is the use of the LIMIT clause in MySQL?

The LIMIT clause is used to restrict the number of rows returned by a SELECT statement. It takes two parameters, the starting row and the number of rows to return, and is often used for pagination purposes.