DAX LEFT Function

The DAX LEFT function in Power BI is used to extract a specified number of characters from the beginning of a text string. This function is particularly useful for retrieving specific parts of a text string, such as extracting a prefix, code, or initial characters from a larger string.

Syntax:

LEFT(<text>, <num_chars>)

<text>: The text string from which you want to extract characters.

<num_chars>: The number of characters to extract from the start of the text string.

Purpose:

The LEFT function helps you to isolate and work with the leading portion of text data. This can be essential for tasks like extracting codes, abbreviations, or other standardized prefixes from text fields.

Example:

Suppose you have a table named "Products" with a column "ProductCode" that contains alphanumeric codes, and you want to extract the first three characters of each product code.

You can use the LEFT function as follows:

Prefix = LEFT(Products[ProductCode], 3)

Example Scenario:

Assume you have the following "Products" table:

Using the LEFT function, you can extract the first three characters of each product code:

Prefix = LEFT(Products[ProductCode], 3)

The resulting table would be:

Handling Edge Cases:

If <num_chars> is greater than the length of <text>, the entire text string is returned.

If <num_chars> is zero or negative, an empty string is returned.

Combining with Other Functions:

You can combine the LEFT function with other DAX text functions to create more complex text manipulations.

Example with RIGHT:

To extract the first three and last three characters of a product code:

FirstThree = LEFT(Products[ProductCode], 3)

LastThree = RIGHT(Products[ProductCode], 3)

                                   

Example with LEN and LEFT:

To extract all but the last character of a product code:

AllButLast = LEFT(Products[ProductCode], LEN(Products[ProductCode]) - 1)

                           

Related Functions:

RIGHT: Returns the specified number of characters from the end of a text string.

MID: Returns a specific number of characters from a text string, starting at the position you specify.

LEN: Returns the number of characters in a text string.

CONCATENATE: Joins two text strings into one.

TRIM: Removes all spaces from a text string except for single spaces between words.

UPPER: Converts a text string to all uppercase letters.

LOWER: Converts a text string to all lowercase letters.

The LEFT function in Power BI is a valuable tool for extracting specific parts of text strings from the beginning. Understanding how to use the LEFT function effectively allows you to perform precise text manipulations and enhance your data analysis capabilities in Power BI.