? DATALENGTH Function in SQL

The DATALENGTH() function returns the number of bytes used to store a value in a column or expression.

? Syntax

DATALENGTH(expression)

• expression: The column or value you want to measure.

? What it Returns

• Number of bytes used to store the data, including trailing spaces for CHAR and VARCHAR.

• Different from LEN() which returns the number of characters (ignoring trailing spaces).

? Example (SQL Server)

SELECT DATALENGTH('Hello World') AS DataLength;  -- Returns 11 (bytes)SELECT DATALENGTH(CAST('Hello' AS VARCHAR(10))) AS DataLength;  -- Returns 5SELECT DATALENGTH(CAST('Hello' AS NVARCHAR(10))) AS DataLength; -- Returns 10 (2 bytes per character)

? Use Cases

• To check storage size of data.

• Useful for binary, varbinary, or string data to find actual bytes used.

If you want examples for other SQL dialects or differences between DATALENGTH() and LEN(), just ask!