github.com/cockroachdb/cockroach@v20.2.0-alpha.1+incompatible/docs/generated/sql/bnf/set_operation.bnf (about)

     1  set_operation ::=
     2  	select_clause 'UNION' ( 'ALL' | 'DISTINCT' |  ) select_clause
     3  	| select_clause 'INTERSECT' ( 'ALL' | 'DISTINCT' |  ) select_clause
     4  	| select_clause 'EXCEPT' ( 'ALL' | 'DISTINCT' |  ) select_clause