The SQL Server DATALENGTH is used to return the number of bytes used to represent a specified expression. The syntax of DATALENGTH is
SELECT DATALENGTH (String_Expression) FROM [Source]
This DATALENGTH function is useful for VARCHAR, NVARCHAR, VARBINARY, TEXT, NTEXT, and IMAGE Data Types because these data types will store the data length. For this example, We are going to use the below-shown table.
SQL DATALENGTH Example
The DATALENGTH Function is used to return the number of bytes used to represent a given expression. The following query will show multiple ways to use it.
In the below two statements, We used the DATALENGTH function to find the data length of both the variables. We also assigned a new name to that result as ‘Data Length’ using the ALIAS Column.
In the next line, We used it directly on the string.
DECLARE @String_Exp VARCHAR(50) SET @String_Exp = 'Learn SQL Server' DECLARE @Str_Exp NVARCHAR(50) SET @Str_Exp = 'Learn SQL Server' SELECT DATALENGTH(@String_Exp) AS 'Data Length' SELECT DATALENGTH(@Str_Exp) AS 'Data Length' --Finding directly SELECT DATALENGTH('SQL Server Tutorial') AS 'Data Length' SELECT DATALENGTH('SQL Server') AS 'Data Length'
The DATALENGTH function also allows you to find the number of bytes in a column. In this example, We are going to find the Data length of a Department Name and Email columns.
SELECT [FirstName] ,[LastName] ,[DepartmentName] ,DATALENGTH([DepartmentName]) AS [Dept Data Length] ,[Email] ,DATALENGTH([Email]) AS [Email Data Length] FROM [Employe]