How can I glue two tables side by side?

If the tables have the same number of rows, you can use the function ^ (fill):

q)t: ([] x: `a`b; y: 1 2)
q)u: ([] z: "YN")
q)t ^ u / works only when count[t] = count[u] 
x y z
-----
a 1 Y
b 2 N
q)