Combining Wildcard Characters
The % and _ symbols can be used in any combination with literal characters. The example in the slide displays the names of all employees whose last names have the letter "o" as the second character.
ESCAPE Identifier
When you need to have an exact match for the actual % and _ characters, use the ESCAPE identifier. This option specifies what the escape character is. If you want to search for strings that contain SA_, you can use the following SQL statement:
SELECT employee_id, last_name, job_id
FROM employees WHERE job_id LIKE '%SA\_%' ESCAPE '\';