LEN (SSIS Expression)
Applies to: 
SQL Server
SSIS Integration Runtime in Azure Data Factory
Returns the number of characters in a character expression. If the string includes leading and trailing blanks, the function includes them in the count. LEN returns identical values for the same string of single and double byte characters.
Syntax
LEN(character_expression)
Arguments
character_expression
Is the expression to evaluate.
Result Types
DT_I4
Remarks
The character_expression argument can be a DT_WSTR, DT_TEXT, DT_NTEXT, or DT_IMAGE data type. For more information, see Integration Services Data Types.
If character_expression is a string literal or a data column with the DT_STR data type, it is implicitly cast to the DT_WSTR data type before LEN performs its operation. Other data types must be explicitly cast to the DT_WSTR data type. For more information, see Cast (SSIS Expression).
If the argument passed to the LEN function has a Binary Large Object Block (BLOB) data type, such as DT_TEXT, DT_NTEXT, or DT_IMAGE, the function returns a byte count.
LEN returns a null result if the argument is null.
Expression Examples
This example returns the length of a string literal. The return result is 12.
LEN("Ball Bearing")
This example returns the difference between the length of values in the FirstName and LastName columns.
LEN(FirstName) - LEN(LastName)
Returns the length of a computer name using the System variable MachineName.
LEN(@MachineName)