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 the
LEFT
function 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.The
LEFT
function 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
Astuce
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 | |
---|---|
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
.