Blueberry Travel Interview Questions and Answers

DBMS stands for Database Management System. It is a software that manages databases and allows users to interact with them.

• DBMS is a software system that allows users to create, retrieve, update, and manage data in a database.

• There are different types of DBMS, such as relational DBMS (RDBMS), object-oriented DBMS (OODBMS), and NoSQL DBMS.

• Examples of popular DBMS include MySQL, Oracle Database, Microsoft SQL Server, and MongoDB.

Use SQL query with COUNT function to get the count of records in the table.

• Use the SQL query: SELECT COUNT(*) FROM table_name;

• Replace 'table_name' with the actual name of the table you want to count records from.

• The COUNT function returns the number of rows that match the specified criteria.

To add a record to a table, you can use SQL INSERT statement.

• Use the INSERT INTO statement followed by the table name

• Specify the column names and values to be inserted

• Example: INSERT INTO employees (id, name, salary) VALUES (1, 'John Doe', 50000)

Joins in SQL are used to combine rows from two or more tables based on a related column between them.

• Joins are used to retrieve data from multiple tables based on a related column.

• Common types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.

• Example: SELECT * FROM table1 INNER JOIN table2 ON table1.column = table2.column;

To update a table, use SQL UPDATE statement with specified column values and conditions.

• Use SQL UPDATE statement to specify the table name and set the new values for columns

• Add a WHERE clause to specify the conditions for which rows to update

• Example: UPDATE table_name SET column1 = value1, column2 = value2 WHERE condition;

Truncate is a DDL operation that removes all rows from a table, while delete is a DML operation that removes specific rows.

• Truncate is faster than delete as it doesn't generate any undo logs or triggers.

• Truncate cannot be rolled back, while delete can be rolled back using the transaction log.

• Truncate resets the identity of the table, while delete doesn't.

• Truncate doesn't fire delete triggers, while delete does.

• Truncate is non-logged operation, while delete is logged operation...read more

Constraints and DDL commands are essential for defining and managing database structures.

• Constraints ensure data integrity and consistency.

• DDL commands are used to create, modify, and delete database objects.

• Examples of constraints include primary keys, foreign keys, and check constraints.

• Examples of DDL commands include CREATE TABLE, ALTER TABLE, and DROP TABLE.