The following query returns the result 'XxyLAST WORD'. LTRIM removes the individual occurrences of 'x' and 'y', and it stops removing characters when it encounters 'X' because 'X' is not in the expr2 argument.
SELECT LTRIM('xyxXxyLAST WORD','xy');
The following query returns the result 'LEFT TRIM'. LTRIM removes the spaces from the left, and it stops removing characters when it encounters 'L' because 'L' is not in the expr2 argument. Since the expr2 argument is not explicitly specified, the default of a single space is used.
SELECT LTRIM(' LEFT TRIM');