[R] Re: R: Mailing Lists

[Jens Nieschulze]

On Wed, 15 Aug 2001, Jan de Leeuw wrote:

> Is it true that append=T does not work in assignTable() in RMySQL ?
> More specifically: I cannot append a data.frame to an existing table
> in a MySQL database, although I can use the same data.frame to
> create a new table.
> Even more specifically:
>  > assignTable(con,"employee",dita,append=T)
> Error in execStatement.MySQLConnection(con, statement, ...) :
>          RS-DBI driver: (could not run statement: Table 'employee' 
> already exists)
> [1] FALSE
Well, appending is implemented in RMySQL_0.4-2.tar.gz
 but a look at
the Code
in R/All.R in that package line 701 revealed that it ALWAYS tries to
create a table
with name=<whatevername>

[snip] line 685:
  sql1 <- paste("create table ", name, "\n(\n\t", sep="")
  sql2 <- paste(paste(names(field.types), field.types), collapse=",\n\t")
  sql3 <- "\n)\n"
  sql <- paste(sql1, sql2, sql3, collapse="")
[.....] line 701:
  rs <- try(dbExecStatement(new.con, sql))
  if(inherits(rs, "Error") || inherits(rs,"try-error")){
    return(F)
  } else close(rs)
[snip]
so sql, which will try to create a new table, is tried, and MySQL
fails, because the tabel already exits

I put these lines 701-.. in an if-clause

 if(!append){
  rs <- try(dbExecStatement(new.con, sql))
  if(inherits(rs, "Error") || inherits(rs,"try-error")){
    return(F)
  } else close(rs)
}

and once I installed the RMySQL package
appending/overwriting a dataframe to existing tables workes for me

> version
         _                
platform i686-pc-linux-gnu
arch     i686             
os       linux-gnu        
system   i686, linux-gnu  
status                    
major    1                
minor    2.0              
year     2000             
month    12               
day      15               
language R                


***********************************************************************
Jens Nieschulze

Institute for Forest Biometrics &	Phone: ++49-551-39-12107
Applied Computer Science		Fax  : ++49-551-39-3465
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GERMANY				http://www.uni-forst.gwdg.de/~jniesch

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