LEFT Function

Matches the leftmost set of characters in a string, as specified by parameter. The string can be specified as a column reference or a string literal.

Since theLEFTfunction matches based on fixed numeric values, changes to the length or structure of a data field can cause your recipe to fail to properly execute.
TheLEFTfunction requires an integer value for the number of characters to match. If you need to match strings using patterns, you should use theSTARTSWITH transform instead. See STARTSWITH Function.

Wrangle vs. SQL: This function is part of Wrangle, a proprietary data transformation language. Wrangle is not SQL. For more information, see Wrangle Language.

Basic Usage

Column reference example:

left(MyName,3)

Output: Returns the first three letters of the MyName column value.

String literal example:

left('Hello, World',5)

Output: Returns the string: Hello.

Syntax and Arguments

left(column_string,char_count)

Argument	Required?	Data Type	Description
column_string	Y	string	Name of the column or string literal to be applied to the function
char_count	Y	integer (positive)	Count of characters from the start of the value to include in the match

For more information on syntax standards, see Language Documentation Syntax Notes.

column_string

Name of the column or string constant to be searched.

Missing string or column values generate missing string results.
String constants must be quoted ('Hello, World').
Multiple columns and wildcards are not supported.

Usage Notes:

Required?	Data Type	Example Value
Yes	String literal or column reference	myColumn

char_count

Count of characters from the start of the string to include in the match.

Value must a non-negative integer. If the value is 0, then the match fails for all strings.
If this value is greater than the length of the string, then the match is the entire string.
References to columns of integer data type are not supported.

Usage Notes:

Required?	Data Type	Example Value
Yes	Integer (non-negative)	5

Examples

提示

For additional examples, see Common Tasks.

Example - Driver's License Type

Source:

A California driver license number is one alphabetical character followed by seven digits (e.g., A1234567). The following is a set of California driver's license values:

LastName	LicenseID
Able	A1234567
Baker	B5555555
Charlie	C0123456

The LicenseID value contains the license class as the first character of the value. For example, Baker's license is a Commercial Class B license.

Transformation:

To extract the license type into a separate column, you can use the following transformation:

Transformation Name	`New formula`
Parameter: Formula type	Single row formula
Parameter: Formula	left(LicenseID,1)

Results:

LastName	LicenseID	left_LicenseID
Able	A1234567	A
Baker	B5555555	B
Charlie	C0123456	C

You can rename the new column to LicenseType.

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