LEFT (SSIS Expression)
Applies to: 
SQL Server
SSIS Integration Runtime in Azure Data Factory
Returns the specified number of characters from the leftmost portion of the given character expression.
Syntax
LEFT(character_expression,number)
Arguments
character_expression
Is a character expression from which to extract characters.
number
Is an integer expression that indicates the number of characters to be returned.
Result Types
DT_WSTR
Remarks
If number is greater than the length of character_expression, the function returns character_expression.
If number is zero, the function returns a zero-length string.
If number is a negative number, the function returns an error.
The number argument can take variables and columns.
LEFT works only with the DT_WSTR data type. A character_expression argument that is a string literal or a data column with the DT_STR data type is implicitly cast to the DT_WSTR data type before LEFT performs its operation. Other data types must be explicitly cast to the DT_WSTR data type. For more information, see Integration Services Data Types and Cast (SSIS Expression).
LEFT returns a null result if either argument is null.
Expression Examples
The following example uses a string literal. The return result is "Mountain".
LEFT("Mountain Bike", 8)