nest_join() returns all rows and columns in x with a new nested-df column that contains all matches from y. When there is no match, the list column is a 0-row tibble.

nest_join()类似left_join()，返回的形式不一样。

band_members %>% nest_join(band_instruments)
#> Joining, by = "name"
#> # A tibble: 3 x 3
#>   name  band    band_instruments
#>   <chr> <chr>   <list>          
#> 1 Mick  Stones  <tibble [0 × 1]>
#> 2 John  Beatles <tibble [1 × 1]>
#> 3 Paul  Beatles <tibble [1 × 1]>

把nest_join之后，band_instruments的结果打印出来

[[1]]
# A tibble: 0 x 1
# … with 1 variable: plays <chr>

[[2]]
# A tibble: 1 x 1
  plays 
  <chr> 
1 guitar

[[3]]
# A tibble: 1 x 1
  plays
  <chr>
1 bass 

对比left_join

> band_members %>% left_join(band_instruments)
Joining, by = "name"
# A tibble: 3 x 3
  name  band    plays 
  <chr> <chr>   <chr> 
1 Mick  Stones  NA    
2 John  Beatles guitar
3 Paul  Beatles bass