SELECT * FROM `mytable` WHERE 
`column1` LIKE 'AAA-123456785%' AND `column2` IS NOT NULL OR 
`column1` LIKE 'AAA-12345678%' AND `column2` IS NOT NULL OR 
`column1` LIKE 'AAA-1234567%' AND `column2` IS NOT NULL OR 
`column1` LIKE 'AAA-123456%' AND `column2` IS NOT NULL

DELIMITER $
DROP PROCEDURE IF EXISTS pr $
CREATE PROCEDURE pr()
BEGIN
    IF (SELECT COUNT(*) FROM `mytable` WHERE `column1` LIKE 'AAA-12345678%' AND `column2` IS NOT NULL) > 0 THEN
    	SELECT * FROM `mytable` WHERE `column1` LIKE 'AAA-12345678%' AND `column2` IS NOT NULL ORDER BY id DESC LIMIT 1;
    END IF;
END $
DELIMITER ;
CALL pr;

DELIMITER $
DROP PROCEDURE IF EXISTS pr $
CREATE PROCEDURE pr()
BEGIN
	SET @myparam='AAA-123456785';    
    SET @i = 3;    
    
    WHILE @i >= 0 DO    
        IF (SELECT COUNT(*) FROM `mytable` WHERE `column1` LIKE CONCAT(@myparam, '%') AND `column2` IS NOT NULL) > 0 THEN
            SELECT * FROM `mytable` WHERE `column1` LIKE CONCAT(@myparam, '%') AND `column2` IS NOT NULL ORDER BY id DESC LIMIT 1;
            SET @i=0;
        END IF;        
        SET @myparam= LEFT(@myparam, CHARACTER_LENGTH(@myparam)-1);
    	SET @i = @i- 1;        
  	END WHILE;
END $
DELIMITER ;
CALL pr;

SELECT mytable.column1
FROM mytable, (SELECT 1 num UNION SELECT 2 ... UNION SELECT 20) nums
WHERE SUBSTRING(mytable.column1 FOR num) = SUBSTRING(@parameter FOR num)
ORDER BY num DESC, mytable.column1 DESC LIMIT 1

SQL запрос: Документация

SELECT mytable.column1
FROM mytable, (SELECT 1 num UNION SELECT 2 ... UNION SELECT 20) nums
WHERE SUBSTRING(mytable.column1 FOR num) = SUBSTRING('AAA-123456785' FOR num)
ORDER BY num DESC, mytable.column1 DESC LIMIT 1

Ответ MySQL: Документация

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '... UNION SELECT 20) nums
WHERE SUBSTRING(mytable.column1 FOR num) = SUBSTRING(' at line 2

DELIMITER $
DROP PROCEDURE IF EXISTS pr $
CREATE PROCEDURE pr(myparam VARCHAR(20))
BEGIN
    SET @i = 3;        
    WHILE @i >= 0 DO    
        IF (SELECT COUNT(*) FROM `mytable` WHERE `column1` LIKE CONCAT(myparam, '%') AND `column2` IS NOT NULL) > 0 THEN
            SELECT * FROM `mytable` WHERE `column1` LIKE CONCAT(myparam, '%') AND `column2` IS NOT NULL ORDER BY id DESC LIMIT 1;
            SET @i=0;
        END IF;        
        SET myparam= LEFT(myparam, CHARACTER_LENGTH(myparam)-1);
    	SET @i = @i- 1;        
    END WHILE;
END $
DELIMITER ;
CALL pr('AAA-123456785');

SELECT * FROM `mytable` WHERE `column1` LIKE CONCAT(LEFT('AAA-123456785', CHARACTER_LENGTH('AAA-123456785')-3), '%') AND `column2` IS NOT NULL ORDER BY `column1` DESC