> lf <- lazy_frame(a = 1:3, b = 3:1)
> rf <- lazy_frame(a = 1:3, c = 4:6)
> # setop
> lf %>% union_all(rf) %>% arrange(a)
<SQL>
SELECT *
FROM ((SELECT `a`, `b`, NULL AS `c`
FROM `df`)
UNION ALL
(SELECT `a`, NULL AS `b`, `c`
FROM `df`)) `dbplyr_001`
ORDER BY `a`

> lf %>% arrange(a) %>% union_all(rf)
<SQL>
(SELECT `a`, `b`, NULL AS `c`
FROM (SELECT *
FROM `df`
ORDER BY `a`) `dbplyr_002`)
UNION ALL
(SELECT `a`, NULL AS `b`, `c`
FROM `df`)

> lf %>% union_all(rf %>% arrange(a))
<SQL>
(SELECT `a`, `b`, NULL AS `c`
FROM `df`)
UNION ALL
(SELECT `a`, NULL AS `b`, `c`
FROM (SELECT *
FROM `df`
ORDER BY `a`) `dbplyr_003`)

