Create an 'inverse' selection from a mysql query -

i have long , complex mysql query on table lot of 'where fieldx '%abc%'' , few 'where fieldx not '%efg%'. without doing bunch of search , replace change not , vice-versa, there simple query can select records not meet large query parameters vs ones designed do?

simple example:

• i have tablea field called letter 26 records, 1 each letter of alphabet.

i have query says:

select * tablea `letter` = 'a' or `letter` = 'b' or `letter` = 'c' or or `letter` = 'd' or `letter` = 'e' or `letter` = 'f' or `letter` not 'g' or `letter` not 'h' 

now instead of doing search , replace reverse/negate of 'where' conditions:

select * tablea `letter` != 'a' or `letter` != 'b' or `letter` != 'c' or or `letter` != 'd' or `letter` != 'e' or `letter` != 'f' or `letter` 'g' or `letter` 'h' 

i want use existing query , same result. thought there might way add select or other modifier select records ones in original select:

select * tablea `letter` != (select * tablea `letter` != 'a' or `letter` != 'b' or `letter` != 'c' or or `letter` != 'd' or `letter` != 'e' or `letter` != 'f' or `letter` not 'g' or `letter` not 'h') 

cleary not sure if last example working mysql goal; encase original query inside end returning of record not selected in original query.

first of all, when inverting comparisons, have change or and, otherwise every record in table. either not 'a' or not 'b'. :)

it should be:

select * tablea `letter` != 'a' , `letter` != 'b' , ... 

back question, think easiest solution enclose entire condition in parentheses , add not operator:

select * tablea not (`letter` = 'a' or `letter` = 'b' or ....)