At present, we do not support SQL MODE which is similar to MySQL. In MySQL, SQL MODE is stored in global session and session with a 64 bit address，and every bit 0 or 1 on this address represents a mode state. Besides, MySQL supports combine mode which is composed of several modes.
We should support SQL MODE to deal with sql dialect problems. We can heuristically use the MySQL way to store SQL MODE in session and parse it into string when we need to return it back to client.
This commit suggests a solution to support SQL MODE. But it's just a sample, and the mode types in SqlModeHelper.java are not really meaningful from now on.
ac5dd0c9f2