sql - Is having an identity primary key in addition to a composite unique constraint redundant? -

i have table has identity column primary key unique constraint on both identity column + second column:

create table variable (     variableid bigint identity(1,1) primary key nonclustered,     calcid bigint not null, ) create unique clustered index cl_calcid_variableid on variable(calcid,variableid) 

i have second table has identity primary key, 2 of same fields first table act foreign keys:

create table value (     valueid bigint identity(1,1) primary key nonclustered,     calcid bigint not null,     variableid bigint not null,     foreign key (calcid,variableid) references variable(calcid, variableid) ) create clustered index cl_calcid_variableid_valueid on value(calcid,variableid,valueid) 

is design redundant?

since variableid identity in first table, don't need foreign key have calcid , variableid in second table. thinking of building tables way though because combination of calcid+variableid "makes sense" describe unique record having identity column makes easier write queries update/delete single row - not sure if over-complicating design.

any thoughts appreciated, thanks.

edit: example data:

variableid  | calcid --------------------- 1           | 1 2           | 1 3           | 1 4           | 2 5           | 2  valueid | variableid    | calcid --------------------------------- 1       | 1             | 1 2       | 1             | 1 3       | 2             | 1 4       | 3             | 1 5       | 4             | 2 6       | 4             | 2 7       | 5             | 2  

as in cases, answer it depends.

keeping identity column surrogate key along side composite unique index idea when using key of table foreign key other tables. simplifies database connections , make joins easier write, read , maintain.

however, if table not referenced other tables, there not sense in adding surrogate key.

also, dnoeth wrote in comment, there no point of making composite unique index when of it's parts unique.