Concatenation
Strings may be concatenated using the concatenation operator having the form
<expr> || <expr>
where <expr> is any expression that results in a string value.
It is an error to concatenate non-string values. Values may be converted to string using a cast to type string.
Examples
Concatenate two fields
# spq
values a || b
# input
{a:"foo",b:"bar"}
{a:"hello, ",b:"world"}
{a:"foo",b:123}
# expected output
"foobar"
"hello, world"
error("incompatible types")
Cast non-string values to concatenate
# spq
values "foo" || 123::string
# input
# expected output
"foo123"