Want to create a trigger to achieve similar to the following functions, but don't know how to solve the limited level, appeal for help for
Create the trigger drop_reader
-> After the update on reader_message for each row
-> The begin
-> Select year from degree_year d
-> Where d.d egree=reader_message. Degree;
-> The select datediff (curdate (), year) as cc.
-> If the cc & gt; Year * 365 then
-> The delete from reader_message
-> Where reader_message. Rname=old. Rname;
-> end if;
-> End//