DESCRIBE FUNCTION like;
DESCRIBE FUNCTION EXTENDED like;

EXPLAIN
SELECT '_%_' LIKE '%\_\%\_%', '__' LIKE '%\_\%\_%', '%%_%_' LIKE '%\_\%\_%', '%_%_%' LIKE '%\%\_\%',
  '_%_' LIKE '\%\_%', '%__' LIKE '__\%%', '_%' LIKE '\_\%\_\%%', '_%' LIKE '\_\%_%',
  '%_' LIKE '\%\_', 'ab' LIKE '\%\_', 'ab' LIKE '_a%', 'ab' LIKE 'a','ab' LIKE '','' LIKE ''
FROM src WHERE src.key = 86;

SELECT '_%_' LIKE '%\_\%\_%', '__' LIKE '%\_\%\_%', '%%_%_' LIKE '%\_\%\_%', '%_%_%' LIKE '%\%\_\%',
  '_%_' LIKE '\%\_%', '%__' LIKE '__\%%', '_%' LIKE '\_\%\_\%%', '_%' LIKE '\_\%_%',
  '%_' LIKE '\%\_', 'ab' LIKE '\%\_', 'ab' LIKE '_a%', 'ab' LIKE 'a','ab' LIKE '','' LIKE ''
FROM src WHERE src.key = 86;


SELECT '1+2' LIKE '_+_', 
       '1+2' LIKE '1+_',
       '112' LIKE '1+_',
       '|||' LIKE '|_|', 
       '+++' LIKE '1+_' 
FROM src LIMIT 1;