Like and the city watch other users association table, then want to user A and user B associated A save of aa and B save bb, can only use the user id has been left to join?

CodePudding user response:

The union can also

CodePudding user response:

He mean it should be the dimension tables or data dictionary tables, a number of different dimensions or attributes on a table, you associate the table many times, this is inevitable, which field will need to link the field corresponding table

reference 1st floor Pcamo response:

union seems to also can