sql server - Count unique numbers in R and SQL -


i have data use in both r , sql server. problem when search unique numbers specific column in r shows 222 , in sql returns 216. what's problem caused difference?

the query used in sql:

select count(distinct colname) tablename

and in r:

length(unique(dataframename$colname))

it's difficult without actual data, r , sql @ unique values differently. r (more point - unique) treat na , various sizes of spaces unique values:

> unique(c("f","g","f","","  ",na,null)) [1] "f"  "g"  ""   "  " na   > length(unique(c("f","g","f","","  ",na,null))) [1] 5

sql treat various sizes of space being equal , non-unique:

create table persons (     personid int,     lastname varchar(255)); insert persons (personid, lastname)        values (1, 'rockwell'),(2,''),(4,'cohen'),(5,' '),(6,'  ');  select count(distinct lastname) persons

will give answer 3

you can trim trailing , leading whitespace str_trim stringr library in r:

library(stringr)  <- str_trim(c("f","g","f","","  ",na,null)) unique(a) [1] "f" "g" ""  na

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