Strip last two characters of a column in MySQL

substring().

http://dev.mysql.com/doc/refman/5.0/en/string-functions.html

To select all characters except the last n from a string (or put another way, remove last n characters from a string); use the SUBSTRING and CHAR_LENGTH functions together:

SELECT col
     , /* ANSI Syntax  */ SUBSTRING(col FROM 1 FOR CHAR_LENGTH(col) - 2) AS col_trimmed
     , /* MySQL Syntax */ SUBSTRING(col,     1,    CHAR_LENGTH(col) - 2) AS col_trimmed
FROM tbl

To remove a specific substring from the end of string, use the TRIM function:

SELECT col
     , TRIM(TRAILING '.php' FROM col)
-- index.php becomes index
-- index.php.php becomes index (!)
-- index.txt remains index.txt

Why not using LEFT(string, length) function instead of substring.

LEFT(col,char_length(col)-2) 

you can visit here https://dev.mysql.com/doc/refman/5.7/en/string-functions.html#function_left to know more about Mysql String Functions.