How to avoid inserting duplicate records in table type sql server for a simple table with two rows key-1 and key-2 -

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i created simple table 2 columns, let's id-1 , id-2.

the combination must unique, solved because primary key.

so 1,1 1,2 1,3 taken care of.

but how can avoid combinations 2,1 , 1,2 , 1,3 , 3,1 not allowed?

create 2 other columns computed based on lowest value of first column, put unique index on 2 computed columns.

    create table [dbo].[test1](     [id1] [int] not null,     [id2] [int] not null,     [id1a]  (case when [id1]<[id2] [id1] else [id2] end),     [id2a]  (case when [id1]>[id2] [id1] else [id2] end),  constraint [pk_test1] primary key clustered  (     [id1a] asc,     [id2a] asc )

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