SQL Data Type

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SQL data types define the kind of data that can be stored in a column of a table, ensuring data integrity, optimizing storage, and improving performance.

👉 Example:
A column storing numbers uses a numeric data type, while a column storing text uses a string data type.

SQL Server data types are mainly divided into these categories:
1️. Numeric Data Types: Numeric data types in SQL Server are used to store numbers such as integers, decimal values, and approximate numeric values.

2️. Character/String Data Types: Character data types are used to store text values such as names, emails, addresses, and descriptions. Examples include CHAR, VARCHAR, NCHAR, and NVARCHAR.

3. Date and Time Data Types: SQL Server provides several date and time data types such as DATE, TIME, DATETIME, DATETIME2, SMALLDATETIME, and DATETIMEOFFSET to store date and time information.

4️. Binary Data Types: Binary data types are used to store binary values like images, files, hashes, or encrypted data. Examples include BINARY, VARBINARY, and VARBINARY(MAX).

5️. Other Special Data Types: Other special SQL Server data types are used for flags, unique IDs, structured XML, mixed-type storage, and spatial data. Examples: BIT, UNIQUEIDENTIFIER, SQL_VARIANT, XML, GEOGRAPHY.

Example: Using Numeric Data Types 

CREATE TABLE Orders (
    OrderID INT,
    CustomerID INT,
    Quantity SMALLINT,
    Rating TINYINT,
    TransactionID BIGINT,
    Price DECIMAL(10,2),
    TotalAmount NUMERIC(10,2),
    Discount FLOAT,
    TaxRate REAL,
    IsDelivered BIT
);

Example: Using Character/String Data Types 

CREATE TABLE Customers (
    CustomerID INT,
    FirstName VARCHAR(50),
    LastName VARCHAR(50),
    Gender CHAR(1),
    CountryCode NCHAR(3),
    Address NVARCHAR(200),
    Email VARCHAR(100),
    Notes VARCHAR(MAX),
    ProfileDescription NVARCHAR(MAX)
);

Example: Using Date and Time Data Types 

CREATE TABLE Orders (
    OrderID INT PRIMARY KEY,
    OrderDate DATE,
    OrderTime TIME,
    OrderDateTime DATETIME,
    DeliveryDateTime DATETIME2,
    ShippingDate SMALLDATETIME,
    CreatedAt DATETIMEOFFSET
);

Example: Using All Binary Data Types 

CREATE TABLE OrderFiles (
    OrderID INT,
    ProductHash BINARY(10),
    ProductImage VARBINARY(200),
    InvoiceFile VARBINARY(MAX)
);

Example: Using Special Data Types 

CREATE TABLE CustomersSpecialTypes (
    CustomerID UNIQUEIDENTIFIER,
    FirstName NVARCHAR(50),
    LastName NVARCHAR(50),
    IsActive BIT,
    CustomerData SQL_VARIANT,
    ProfileXML XML,
    Location GEOGRAPHY
);


Simple Exam/Interview Definition
In SQL Server, data types define the type of values that can be stored in a table column, such as numbers, text, dates, or binary data.

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