# Correcciones de RODBC
sqlFetch <- function (channel, sqtable, ..., colnames = FALSE, rownames = TRUE)
{
    if (!odbcValidChannel(channel))
    stop("first argument is not an open RODBC channel")
    if (missing(sqtable))
    stop("Missing argument 'sqtable'")
    dbname <- odbcTableExists(channel, sqtable)
    DBMS <- odbcGetInfo(channel)[1]
    if (DBMS == "ACCESS" && length(grep(" ", dbname)))
    dbname <- paste("[", dbname, "]", sep = "")
    ans <- sqlQuery(channel, paste("SELECT * FROM", dbname),
        ...)
    if (is.data.frame(ans)) {
        if (is.logical(colnames) && colnames) {
            colnames(ans) <- as.character(as.matrix(ans[1, ]))
            ans <- ans[-1, ]
        }
        if (is.logical(rownames) && rownames) rownames <- "rownames"
        if (is.character(rownames)) {
            cn <- names(ans)
            if (!is.na(rn <- match(rownames, cn))) {
                row.names(ans) <- as.character(ans[, rn])
                ans <- ans[, -rn, drop = FALSE]
            }
        }
    }
    ans
}

odbcValidChannel <- function (channel)
{
    inherits(channel, "RODBC") && is.integer(channel) && .Call("RODBCcheckchannel",
        channel, attr(channel, "id"), PACKAGE = "RODBC") > 0
}
odbcTableExists <- function (channel, tablename, abort = TRUE)
{
    if (!odbcValidChannel(channel))
        stop("first argument is not an open RODBC channel")
    if (length(tablename) != 1)
        stop(paste(tablename, "should be a name"))
    tablename <- as.character(tablename)
    switch(attr(channel, "case"), nochange = {
    }, toupper = tablename <- toupper(tablename), tolower = tablename <- tolower(tablename))
    res <- sqlTables(channel)
    tables <- if (is.data.frame(res))
        res[, 3]
    else ""
    stables <- sub("\\$$", "", tables)
    ans <- tablename %in% stables
    if (abort && !ans)
        stop(paste(tablename, ": table not found on channel"))
    if (ans) {
        dbname <- tables[match(tablename, stables)]
        if (tablename != dbname)
            paste("[", tablename, "$]", sep = "")
        else tablename
    }
    else character(0)
}
# Final de correcciones de RODBC