R/tcplListFlds.R

In daynefiler/tcpl: ToxCast Data Analysis Pipeline

#-------------------------------------------------------------------------------
# tcplListFlds: Load the column/field names from the given table and database  
#-------------------------------------------------------------------------------

#' @title Load the field names for a table
#' @description
#' \code{tcplListFlds} loads the column names for the given table and database.
#' 
#' @param tbl Character of length 1, the tcpl database table
#' @param db Character of length 1, the tcpl database
#' 
#' @details 
#' This function can be particularly useful in defining the 'fld' param in the
#' tcplLoad- functions.
#' 
#' @examples 
#' ## Gives the fields in the mc1 table
#' tcplListFlds("mc1")
#' 
#' @return A string of field names for the given table.
#' 
#' @import data.table
#' @export


tcplListFlds <- function(tbl, db = getOption("TCPL_DB")) {
  
  ## Variable-binding to pass R CMD Check
  name <- COLUMN_NAME <- NULL
  
  if (length(tbl) > 1 | length(db) > 1) {
    stop("tbl and db must both be of length 1.")  
  } 
  
  if (getOption("TCPL_DRVR") == "SQLite") {
    
    qformat <- "PRAGMA table_info(%s);" 
    qstring <- sprintf(qformat, tbl)
    return(tcplQuery(qstring, db)[ , name])
    
  }
  
  if (getOption("TCPL_DRVR") == "MySQL") {
    
    qformat <- 
      "
      SELECT 
        `COLUMN_NAME` 
      FROM 
        `INFORMATION_SCHEMA`.`COLUMNS` 
      WHERE 
        `TABLE_SCHEMA` = '%s' 
        AND 
        `TABLE_NAME` = '%s';
      "
    
    return(tcplQuery(sprintf(qformat, db, tbl), db)[ , COLUMN_NAME])
    
  }
  
  stop(getOption("TCPL_DRVR"), " is not a supported database system. See ",
       "?tcplConf for more details.")
  
}

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