Maybe try combining them into a single array then performing array comparisons...
On Wednesday, March 22, 2017, Glen Huang <hey....@gmail.com> wrote: > Thanks. > > Didn't realize it could be implemented with a exclusion constraint. The > comparing between any two row definitely sounds like the right direction. > But I'm still having a hard time figuring out how i should write the > `exclude_element WITH operator` part, which I think, should detect if > specified columns consist of the same items, regardless the order? could > `exclude_element` contains multiple columns? (from the syntax it looks like > it's impossible) And is there such an operator to compare multiple columns? > > On 23 Mar 2017, at 1:04 AM, David G. Johnston <david.g.johns...@gmail.com > <javascript:_e(%7B%7D,'cvml','david.g.johns...@gmail.com');>> wrote: > > On Wed, Mar 22, 2017 at 9:54 AM, Glen Huang <hey....@gmail.com > <javascript:_e(%7B%7D,'cvml','hey....@gmail.com');>> wrote: > >> Hello, >> >> If I have a table like >> >> CREATE TABLE relationship ( >> obj1 INTEGER NOT NULL REFERENCES object, >> obj2 INTEGER NOT NULL REFERENCES object, >> obj3 INTEGER NOT NULL REFERENCES object, >> ... >> ) >> >> And I want to constrain that if 1,2,3 is already in the table, rows like >> 1,3,2 or 2,1,3 shouldn't be allowed. >> >> Is there a general solution to this problem? >> >> Sorry if the question is too basic, but I couldn't find the answer in the >> doc, at least not in the chapter on unique index. >> > > The most direct option to consider is a exclusion constraint. > > https://www.postgresql.org/docs/current/static/ddl-constraints.html > (bottom of page) > > David J. > > >
