DATA TYPES IN SQL

1. Numeric Data Types

• Integer: A whole number without a decimal point.
• Decimal: A number with a decimal point.
• Floating-point: A number with a decimal point and a fractional part.

2. Character Data Types

• Char: A fixed-length character string.
• Varchar: A variable-length character string.
• Nchar: A fixed-length Unicode character string.
• Nvarchar: A variable-length Unicode character string.

3. Date and Time Data Types

• Date: A date without a time.
• Time: A time without a date.
• DateTime: A date and time.
• Smalldatetime: A date and time with a precision of 3.33 milliseconds.
• Datetime2: A date and time with a precision of 7.00 milliseconds.

4. Other Data Types

• Binary: A binary string.
• Varbinary: A variable-length binary string.
• Image: A large binary string.
• UniqueIdentifier: A unique identifier.
• Cursor: A pointer to a set of rows.
• Rowversion: A value that changes whenever a row is updated.
• XML: An XML document.

The data type of a column defines what value the column can hold. For example, an integer column can only hold whole numbers, while a varchar column can hold any string of characters.

When you create a table, you must specify the data type for each column. For example, the following statement creates a table with two columns:

CREATE TABLE customers (

  id INT,

  name VARCHAR(255)

);

The id column is an integer column, and the name column is a varchar column with a maximum length of 255 characters.

You can also change the data type of a column after the table has been created. For example, the following statement changes the data type of the name column to nvarchar:

ALTER TABLE customers

ALTER COLUMN name NVARCHAR(255);