I am getting a strange error message 1493 - "SQL parameter is missing" when passing a long SQL Statement.
Driver MySQL 5.1, Database MySQL. The statement is around 13400 characters long.

is there a limit, or can that limit be changed? I thought the limit would be much larger, and the error message would then also be different (statement too long).

I copied the SQL command in MySQL Workbench and there it executes well. Only work around is to split the command and append the results, but of course that would be slower than to run the unions in one pass.