TOP 100 PERCENT is issued for MSSQL in absence of ORDER BY, breaking support for Azure DW #337
Description
PR #277 causes the mssql backend to issue SELECT TOP 100 PERCENT in sub queries even if there is no ORDER BY clause. This breaks dbplyr for Azure Data Warehouse, which is a version of MSSQL that does not support SELECT [...] PERCENT syntax. I'm working on a PR to change this so that TOP 100 PERCENT at least only gets issued if there is actually an ORDER BY, so that ADW users can use dbplyr again.
mf <- lazy_frame(x = 1:3, con = simulate_mssql())
mf %>% mutate(x = -x) %>% mutate(x = -x) %>% sql_render()
#> <SQL> SELECT -`x` AS `x`
#> FROM (SELECT TOP 100 PERCENT -`x` AS `x`
#> FROM `df`) `dbplyr_001`