In access, you can set the sid field to automatic numbering. You don't need to fill it out. Every time a new record is added, the sid will automatically become+1. Sqlserver has something similar, but it is more complicated. Mysql hasn't touched it. It should be about the same.

The statement "insert into s _ table (sid, sname, stype) values (s _ max+ 1,' Zhang San',' new user') does not need to add a sid field, but only needs to be written as insert into s _ table (sname, stype) values ('Zhang San',' new'). Sid will write it himself, automatically+1.