SQL queries are instructions written in Structured Query Language (SQL) that are used to communicate with a relational database management system (RDBMS). In DBMS and C++ Lab, SQL queries are important because they provide a systematic way to create databases, store data, retrieve required information, modify existing records, and control access to database resources. SQL is widely used with database systems such as MySQL, Oracle, PostgreSQL, and SQL Server. A C++ program can also interact with a database by sending SQL queries through suitable database connectivity libraries or APIs. Therefore, understanding SQL queries is essential for developing database-oriented applications in C++. SQL is generally divided into several categories according to the purpose of the commands. Data Definition Language (DDL) is used to define and modify the structure of database objects. Common DDL commands include `CREATE`, `ALTER`, `DROP`, and `TRUNCATE`. For example, a table named `Student` can be created using: ```sql CREATE TABLE Student ( Student_ID INT PRIMARY KEY, Name VARCHAR(50), Course VARCHAR(30), Marks INT ); ``` This query creates a table with four columns. `Student_ID` is declared as the primary key, which uniquely identifies each student. The `VARCHAR` data type stores character values, while `INT` stores integer values. In a C++ Lab application, such a table could be used to store information entered by students through a program. The `ALTER` command is used to modify the structure of an existing table. For example: ```sql ALTER TABLE Student ADD Email VARCHAR(100); ``` This query adds an `Email` column to the `Student` table. The `DROP` command permanently removes a database object, while `TRUNCATE` removes all records from a table without normally removing the table structure. Data Manipulation Language (DML)