In DB2, data types define the type of data that can be stored in a table's column. They ensure that only valid data is stored in the database and help optimize storage and retrieval. DB2 supports a wide range of data types, grouped into categories such as numeric, string, date/time, and large objects (LOBs).

Numeric Data Types -

Data Type	Description	Example
INTEGER (INT)	Stores whole numbers (positive or negative)	INT column to store Employee_ID = 101
SMALLINT	Stores smaller whole numbers, requiring less storage	SMALLINT column for Age = 25
BIGINT	Stores very large integers	BIGINT for tracking high-value counters like Population = 1000000000
DECIMAL (DEC)	Stores fixed-point numbers with precision	DEC(10,2) for Salary = 50000.75
FLOAT/DOUBLE	Stores approximate floating-point numbers	FLOAT for scientific data like Temperature = 36.6

String Data Types -

String data types store text or character data, such as names, addresses, or descriptions.

Data Type	Description	Example
CHAR (n)	Stores fixed-length text	CHAR(5) for storing Country_Code = 'IND'
VARCHAR (n)	Stores variable-length text	VARCHAR(50) for Name = 'Alice'
CLOB (Character Large Object)	Stores large text data (e.g., documents)	CLOB for storing articles or descriptions.
GRAPHIC / VARGRAPHIC	Stores fixed/variable-length graphic strings (e.g., for non-English characters)	Used for multi-language names.

Date and Time Data Types -

These data types store date, time, and timestamp information. They are useful for tracking events, deadlines, and timestamps.

Data Type	Description	Example
DATE	Stores date in YYYY-MM-DD format	DATE column for Hire_Date = '2024-10-25'
TIME	Stores time in HH:MM:SS format	TIME for Start_Time = '09:00:00'
TIMESTAMP	Stores date and time with fractional seconds	TIMESTAMP for Order_Placed = '2024-10-25 10:15:30.123'

Large Object (LOB) Data Types -

LOB types store large amounts of data, such as images, videos, or long text.

Data Type	Description	Example
BLOB (Binary Large Object)	Stores large binary data (e.g., images)	BLOB for storing a product image
CLOB (Character Large Object)	Stores large text data (e.g., documents)	CLOB for storing reports.
DBCLOB (Double-Byte Character Large Object)	Stores double-byte character text (e.g., multi-language content)	DBCLOB for Chinese or Japanese text.

Boolean Data Type -

Data Type	Description	Example
BOOLEAN	Stores true/false values, often used for flags	TRUE or FALSE

XML Data Type -

Data Type	Description	Example
XML	Used to store XML documents and data in XML format	Order_Details column stores order information in XML format

User-Defined Data Types (UDTs) -

DB2 allows the creation of custom data types based on existing types. This provides more control over the kind of data stored. Example - The PhoneNumber data type ensures all phone numbers follow a specific format.

CREATE DISTINCT TYPE PhoneNumber AS CHAR(10);
CREATE TABLE Contacts (
    Contact_ID INT PRIMARY KEY,
    Phone PhoneNumber
);

Each data type serves a specific purpose, from storing numbers and text to managing large objects and timestamps. Choosing the right data types ensures data integrity and optimal performance.

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