MySQL Left() or SUBSTRING()?

Question

Both of these queries will produce same result. But which one is better, faster.

SELECT LEFT(textField, 100) AS first100Chars

SELECT SUBSTRING(textField, 1, 100 )

Thanks.

Answer 1

By itself there is little difference, however left can potentially utilize an index while substring cannot.

Answer 2

Substring will take little more time than left function. Though your case is straight forward use left function only.