A database in Microsoft® SQL Server™ consists of a collection of tables that stores a specific set of structured data. A table contains a collection of rows (sometimes referred to as records or tuples) and columns (sometimes referred to as attributes). Each column in the table is designed to store a certain type of information (for example, dates, names, dollar amounts, or numbers). Tables have several types of controls (constraints, rules, triggers, defaults, and customized user data types) that ensure the validity of the data. Tables can have indexes, much like those in books, that allow rows to be found quickly. Declarative referential integrity (DRI) constraints can be added to the tables to ensure that interrelated data in different tables remains consistent. A database can also store procedures that use Transact-SQL programming code to perform operations with the data in the database, such as storing views that provide customized access to table data.
For example, you can create a database named MyCoDb to manage your company’s data. In the MyCoDb database, you can create a table named Employees to store information about each employee, and the table can contain columns named EmpId, LastName, FirstName, Dept, and Title. You can add some constraints to the table to ensure that no two employees share the same EmpId and that the Dept column contains only valid numbers for the departments in your company. You can define indexes to ensure that you can quickly find the data for an employee based on the employee ID or last name. You will need to add a row of data to the Employees table for each employee so that you can create a procedure named AddEmployee that is customized to accept the data values for a new employee and performs the operation of adding the row to the Employees table. You can define a view called DeptEmps that combines data from the Departments and Employees tables and produces output with a departmental summary of employees.