auto-increment feature

Hi: This is my first day using Maria DB and pardon me if my question is elementary. I am trying to use the Auto_increment option: CREATE TABLE synonym ( meddra_version_no VARCHAR(6) NOT NULL, synonym_id BIGINT NOT NULL AUTO_INCREMENT, llt_id BIGINT NOT NULL, update_user_id VARCHAR(100) NOT NULL, update_timestamp TIMESTAMP NOT NULL DEFAULT now(), CONSTRAINT xpksynonym PRIMARY KEY (meddra_version_no,synonym_id), CONSTRAINT R_79 FOREIGN KEY (meddra_version_no) REFERENCES meddra_version (meddra_version_no), CONSTRAINT R_67 FOREIGN KEY (meddra_version_no, llt_id) REFERENCES llt (meddra_version_no, llt_id) ) [ma-3.1.3][10.4.6-MariaDB]Incorrect table definition; there can be only one auto column and it must be defined as a key Execution Failed! Does this mean that the column that is defined to auto-increment cannot be part of a composite PK? I even tried creating an unique index just on Synonym_id but that does not seem to work either. So, do I have to use the sequence to generate the value of the column? Venki

ps: I had posted my question in a different forum topic. Sorry.