datalength-transact-sql.md

title	DATALENGTH (Transact-SQL) | Microsoft Docs
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ms.date	08/20/2019
ms.prod	sql
ms.prod_service	database-engine, sql-database, sql-data-warehouse, pdw
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ms.technology	t-sql
ms.topic	language-reference
f1_keywords	DATALENGTH_TSQL DATALENGTH
dev_langs	TSQL
helpviewer_keywords	number of bytes representing expression data types [SQL Server], length DATALENGTH function expressions [SQL Server], length lengths [SQL Server], data
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author	pmasl
ms.author	mikeray
monikerRange	>=aps-pdw-2016||=azuresqldb-current||=azure-sqldw-latest||>=sql-server-2016||=sqlallproducts-allversions||>=sql-server-linux-2017||=azuresqldb-mi-current

DATALENGTH (Transact-SQL)

[!INCLUDEtsql-appliesto-ss2008-all-md]

This function returns the number of bytes used to represent any expression.

Note

To return the number of characters in a string expression, use the LEN function.

Transact-SQL Syntax Conventions

Syntax

DATALENGTH ( expression )   

Arguments

expression
An expression of any data type.

Return types

bigint if expression has an nvarchar(max), varbinary(max), or varchar(max) data type; otherwise int.

Remarks

DATALENGTH becomes really helpful when used with data types that can store variable-length data, such as:

• image
• ntext
• nvarchar
• text
• varbinary
• varchar

For a NULL value, DATALENGTH returns NULL.

Note

Compatibility levels can affect return values. See ALTER DATABASE Compatibility Level (Transact-SQL) for more information about compatibility levels.

Note

Use the LEN to return the number of characters encoded into a given string expression, and DATALENGTH to return the size in bytes for a given string expression. These outputs may differ depending on the data type and type of encoding used in the column. For more information on storage differences between different encoding types, see Collation and Unicode Support.

Examples

This example finds the length of the Name column in the Product table:

USE AdventureWorks2016  
GO
SELECT length = DATALENGTH(EnglishProductName), EnglishProductName  
FROM dbo.DimProduct  
ORDER BY EnglishProductName;  
GO  

See also

LEN (Transact-SQL)
CAST and CONVERT (Transact-SQL)
Data Types (Transact-SQL)
System Functions (Transact-SQL)