LEFT

In Lakehouse, the LEFT function is used to extract a specified number of characters from the left side of a given string. It is important to note that the unit of character length is utf8 characters, which means that a Chinese character will be considered as one length unit.

Syntax

The syntax format of the LEFT function is as follows:

LEFT(str, len)

• str: The string from which characters are to be extracted. This parameter accepts data of type VARCHAR.
• len: The number of characters to be extracted from the left side of the string. This parameter should be a positive integer.

Return Value

The LEFT function returns a string containing the specified number of characters extracted from the left side of the input string. The return value's data type is VARCHAR.

Example

Below are several usage examples of the LEFT function:

Example 1:

SELECT LEFT('Hello, welcome to Lakehouse', 5);

This query will return the first 5 characters on the left side of the string 'Hello, welcome to Lakehouse', which is 'Hello'.

Example 2：

SELECT LEFT('Lakehouse，一个强大的实时数据仓库。', 9);

This query will return the first 9 characters from the left side of the string 'Lakehouse，一个强大的实时数据仓库。', which is 'Lakehouse'.

Example 3：

SELECT LEFT('The quick brown fox jumps over the lazy dog', 9);

This query will return the first 9 characters from the left side of the string 'The quick brown fox jumps over the lazy dog', which is 'The quick'.

Notes

• Ensure that the len parameter is a positive integer, otherwise the function will return an error.
• If the len parameter is greater than the length of the input string, the LEFT function will return the entire input string.