尝试写入永久表时，copy_to不适用于非默认模式

Question

I'm trying to use copy_to to write a table to SQL Server 2017 permanently (ie temporary = FALSE). It works on the default schema, but it does not work when I specify a schema other than the default schema. I get a curious error message:

Error: <SQL> 'UPDATE STATISTICS EXISTING_SCHEMA.newTblIris' nanodbc/nanodbc.cpp:1587: 42S02: [Microsoft][ODBC SQL Server Driver][SQL Server]Table 'newTblIris' does not exist.

It is curious because it is obvious the table does not exist. I am trying to create the table.

library(odbc)
library(dbplyr)
library(dplyr)
library(DBI)

con <- dbConnect(odbc(),
                 Driver = "SQL SERVER",
                 Server = "SERVER_NAME",
                 Database = "DB_NAME",
                 UID = "USER_ID",
                 PWD = "PASSWORD")

# works, can write this table to the default schema
copy_to(con, iris, "newTblIris", temporary = FALSE)

# successfully create temporary table in non-default schema
copy_to(con, iris, in_schema("EXISTING_SCHEMA", "newTblIris"))

# does not work and gives above error message
copy_to(con, iris, in_schema("EXISTING_SCHEMA", "newTblIris"), temporary = FALSE)

I have tried the "proper" way to write non-temporary tables following guidance from RStudio, https://db.rstudio.com/best-practices/schema/#write-non-temporary-tables , however when I try their method I also get an error.

dbWriteTable(con, SQL("EXISTING_SCHEMA.iris"), iris)

This gives an error Error: Can't unquote EXISTING_SCHEMA.iris

- Session info --------------------------------------------------------------------------------------------------------------------
 setting  value                       
 version  R version 3.5.2 (2018-12-20)
 os       Windows Server >= 2012 x64  
 system   x86_64, mingw32             
 ui       RStudio                     
 language (EN)                        
 collate  English_United States.1252  
 ctype    English_United States.1252  
 tz       America/New_York            
 date     2019-03-05                  

- Packages ------------------------------------------------------------------------------------------------------------------------
 package     * version date       lib source        
 assertthat    0.2.0   2017-04-11 [1] CRAN (R 3.5.2)
 backports     1.1.3   2018-12-14 [1] CRAN (R 3.5.2)
 bit           1.1-14  2018-05-29 [1] CRAN (R 3.5.2)
 bit64         0.9-7   2017-05-08 [1] CRAN (R 3.5.2)
 blob          1.1.1   2018-03-25 [1] CRAN (R 3.5.2)
 callr         3.1.1   2018-12-21 [1] CRAN (R 3.5.2)
 cli           1.0.1   2018-09-25 [1] CRAN (R 3.5.2)
 crayon        1.3.4   2017-09-16 [1] CRAN (R 3.5.2)
 DBI         * 1.0.0   2018-05-02 [1] CRAN (R 3.5.2)
 dbplyr      * 1.3.0   2019-01-09 [1] CRAN (R 3.5.2)
 desc          1.2.0   2018-05-01 [1] CRAN (R 3.5.2)
 devtools      2.0.1   2018-10-26 [1] CRAN (R 3.5.2)
 digest        0.6.18  2018-10-10 [1] CRAN (R 3.5.2)
 dplyr       * 0.8.0.1 2019-02-15 [1] CRAN (R 3.5.2)
 fs            1.2.6   2018-08-23 [1] CRAN (R 3.5.2)
 glue          1.3.0   2018-07-17 [1] CRAN (R 3.5.2)
 hms           0.4.2   2018-03-10 [1] CRAN (R 3.5.2)
 magrittr      1.5     2014-11-22 [1] CRAN (R 3.5.2)
 memoise       1.1.0   2017-04-21 [1] CRAN (R 3.5.2)
 odbc        * 1.1.6   2018-06-09 [1] CRAN (R 3.5.2)
 pillar        1.3.1   2018-12-15 [1] CRAN (R 3.5.2)
 pkgbuild      1.0.2   2018-10-16 [1] CRAN (R 3.5.2)
 pkgconfig     2.0.2   2018-08-16 [1] CRAN (R 3.5.2)
 pkgload       1.0.2   2018-10-29 [1] CRAN (R 3.5.2)
 prettyunits   1.0.2   2015-07-13 [1] CRAN (R 3.5.2)
 processx      3.2.1   2018-12-05 [1] CRAN (R 3.5.2)
 ps            1.3.0   2018-12-21 [1] CRAN (R 3.5.2)
 purrr         0.3.0   2019-01-27 [1] CRAN (R 3.5.2)
 R6            2.4.0   2019-02-14 [1] CRAN (R 3.5.2)
 Rcpp          1.0.0   2018-11-07 [1] CRAN (R 3.5.2)
 remotes       2.0.2   2018-10-30 [1] CRAN (R 3.5.2)
 rlang         0.3.1   2019-01-08 [1] CRAN (R 3.5.2)
 rprojroot     1.3-2   2018-01-03 [1] CRAN (R 3.5.2)
 sessioninfo   1.1.1   2018-11-05 [1] CRAN (R 3.5.2)
 tibble        2.0.1   2019-01-12 [1] CRAN (R 3.5.2)
 tidyselect    0.2.5   2018-10-11 [1] CRAN (R 3.5.2)
 usethis       1.4.0   2018-08-14 [1] CRAN (R 3.5.2)
 withr         2.1.2   2018-03-15 [1] CRAN (R 3.5.2)

Answer 1

I encountered a similar problem and developed the following work around. This is the core of a function I use to write R tables to the database (the full function can be found in my dbplyr helpers repo ). This cut down version assumes the table you are writing to already exists.

copy_r_to_sql = function(db_connection, schema, sql_table_name, r_table,
                         named_list_of_columns){

  # trim r table to just variables of interest
  r_table = r_table %>%
    select(names(named_list_of_columns))

  # if column type is character or date, wrap in single quotes
  # so SQL reads it as character string
  for(coln in colnames(r_table)){
    col_type = named_list_of_columns[[coln]]
    of(grepl("char", col_type) | grepl("date", col_type))
    r_table[coln] = apply(r_table[coln], 1, function(x) paste0("'", as.character(x), "'"))
  }

  # SQL
  sql_cols = paste0("([",paste0(names(named_list_of_columns), collapse = "],["), "])")
  sql_values = paste0(apply(r_table, 1, 
                            function(x) paste0("(", paste0(x, collapse = ","),")")),
                      collapse = ",\n")

  my_sql = build_sql(con = db_connection,
                     "INSERT INTO ", sql(schema), ".",sql(sql_table_name),"\n",
                     sql(sql_cols), "\n",
                     "VALUES ", sql(sql_values),";")

  result = dbExecute(db_connection, as.character(my_sql))
}

The function is designed to write the SQL text that would add the specified rows to your table. To understand what the function does you can replace the last line dbExecute with a print statement.

By way of an example function call:

named_list_of_columns = list(Sepal.Length = "[float](5,1) NOT NULL",
                             Sepal.Width = "[float](5,1) NOT NULL",
                             Species = "[varchar](15) NOT NULL")

copy_r_to_sql(con, "DB_NAME.SCHEMA", "newTblIris", iris, named_list_of_columns)

I have not tried using this for large tables. If you needed to load a large number of rows, I recommend creating a new table and appending to it in batches.