SQL Server Interview Question #21

What are data types in SQL Server?

Data Types, Keys & Constraints Junior Beginner

Detailed Explanation

A data type defines what kind of value a column, variable, or parameter can store. Choosing the correct data type improves data integrity, storage efficiency, indexing, and query performance.

Common SQL Server data types include INT and BIGINT for integers; DECIMAL for exact numeric values; VARCHAR and NVARCHAR for text; DATE, DATETIME2, and TIME for date/time values; BIT for Boolean-style values; UNIQUEIDENTIFIER for GUIDs; and VARBINARY for binary data.

In production systems, use the smallest appropriate type that correctly represents the business data.

Code Example

CREATE TABLE Products
(
    Id INT IDENTITY(1,1) PRIMARY KEY,
    Name NVARCHAR(200) NOT NULL,
    Price DECIMAL(18,2) NOT NULL,
    IsActive BIT NOT NULL,
    CreatedAt DATETIME2 NOT NULL
);