I found many question, But no solutions.
An index can not be used to speed up queries where the search criteria starts with a wildcard:
LIKE '%text%'
An index can (and might be, depending on selectivity) used for search terms of the form:
LIKE 'text%'
So this means I simply cant use a full wildcard in a big table?
Exactly. Which is why some databases use alternative indexing mechanisms for text. SQL Server has a full text indexing capability that works by breaking the string into WORDS, removing bad ones (like "in" in english - happens too often) and then uses a different syntax for finding words in the text index.
Standard SQL Indices are simply not suited for the task.
MySQL, from a 30 second run in google, also seems to have a full text search mechanism.
