Unions

Union of a pair of tables (or table-likes) is another base operation in queries. Conceptually, it's just lazy "concating" table-likes to get a combinedview.

"Union all" union is defined using the verb ua:

o) t1:+`a`b`c!(1 2;3 4;5 6);
o) t2:+`a`b`c!(10 20;30 40;50 60);
o) u:ua[t1;t2];
o) 0N#.(?[u; (); 0b; `a`b`c!`a`b`c])
a  b  c
--------
1  3  5
2  4  6
10 30 50
20 40 60

Of course, unioning several table-likes is supported as well:

o) t1:+`a`b`c!(1 2;3 4;5 6);
o) t2:+`a`b`c!(10 20;30 40;50 60);
o) t3:+`a`b`c!(100 200;300 400;500 600);
o) s3:?[t3;();0b;`a`b`c!`a`b`c];
o) u:ua/(t1;t2;s3);
o) 0N#.(?[u; (); 0b; `a`b`c!`a`b`c])
a   b   c
-----------
1   3   5
2   4   6
10  30  50
20  40  60
100 300 500
200 400 600

Perhaps unsurprisingly, any other expression accepting table-like works for unions as well. e.g. joining (don't forget aliases):

o) t1:+`a`b`c!(1 2 3;4 5 6;7 8 9);
o) t2:+`a`b`c!(10 20;30 40;50 60);
o) t3:+`a`b`c!(1 10 20;100 300 400;200 500 600);
o) u1:ua[t1;t2];
o) j:ij[(`u1;u1);(`t3;t3);(~`u1`a;~`t3`a)];
o) 0N#.(?[j; (); 0b; `a`b`c!(~`u1`a;~`u1`b;~`t3`c)])
a  b  c
---------
1  4  200
10 30 500
20 40 600