Question

在R中，如何将多行文本文件（包含SQL）的内容导入单个字符串？

sql.txt文件如下所示：

SELECT TOP 100 
 setpoint, 
 tph 
FROM rates

我需要将该文本文件导入R字符串，使其如下所示：

> sqlString
[1] "SELECT TOP 100 setpoint, tph FROM rates"

这样我可以像这样把它送到RODBC

> library(RODBC)
> myconn<-odbcConnect("RPM")
> results<-sqlQuery(myconn,sqlString)

我已经尝试了如下的readLines命令，但它没有提供RODBC所需的字符串格式。

> filecon<-file("sql.txt","r")
> sqlString<-readLines(filecon, warn=FALSE)
> sqlString
[1] "SELECT TOP 100 "                              "\t[Reclaim Setpoint Mean (tph)] as setpoint, "
[3] "\t[Reclaim Rate Mean (tph)] as tphmean "       "FROM [Dampier_RC1P].[dbo].[Rates]"           
>

Answer 1

多功能paste()命令可以使用参数collapse=""执行此操作：

lines <- readLines("/tmp/sql.txt")
lines
[1] "SELECT TOP 100 " " setpoint, "     " tph "           "FROM rates"     

sqlcmd <- paste(lines, collapse="")
sqlcmd
[1] "SELECT TOP 100  setpoint,  tph FROM rates"

Answer 2

下面是一个R函数，它读入多行SQL查询（来自文本文件）并将其转换为单行字符串。该功能删除格式和整行注释。

要使用它，请运行代码来定义函数，单行字符串将是运行的结果 ONELINEQ（＆＃34; querytextfile.sql＆＃34;＆＃34;〜/路径/到/ thefile＆＃34）。

工作原理：内联评论详细说明了这一点;它读取查询的每一行并删除（无需替换）写出单行版本查询所需的任何内容（如问题中所要求的）。结果是一个行列表，其中一些是空白的并被过滤掉;最后一步是将此（未列出）列表粘贴在一起并返回单行。

＃

# This set of functions allows us to read in formatted, commented SQL queries
# Comments must be entire-line comments, not on same line as SQL code, and begun with "--"
# The parsing function, to be applied to each line:
LINECLEAN <- function(x) {
  x = gsub("\t+", "", x, perl=TRUE); # remove all tabs
  x = gsub("^\\s+", "", x, perl=TRUE); # remove leading whitespace
  x = gsub("\\s+$", "", x, perl=TRUE); # remove trailing whitespace
  x = gsub("[ ]+", " ", x, perl=TRUE); # collapse multiple spaces to a single space
  x = gsub("^[--]+.*$", "", x, perl=TRUE); # destroy any comments
  return(x)
}
# PRETTYQUERY is the filename of your formatted query in quotes, eg "myquery.sql"
# DIRPATH is the path to that file, eg "~/Documents/queries"
ONELINEQ <- function(PRETTYQUERY,DIRPATH) { 
  A <- readLines(paste0(DIRPATH,"/",PRETTYQUERY)) # read in the query to a list of lines
  B <- lapply(A,LINECLEAN) # process each line
  C <- Filter(function(x) x != "",B) # remove blank and/or comment lines
  D <- paste(unlist(C),collapse=" ") # paste lines together into one-line string, spaces between.
  return(D)
}
# TODO: add eof newline automatically to remove warning
#############################################################################################

Answer 3

这是我正在使用的最终版本。谢谢Dirk。

fileconn<-file("sql.txt","r")           
sqlString<-readLines(fileconn)          
sqlString<-paste(sqlString,collapse="")
gsub("\t","", sqlString)
library(RODBC)
sqlconn<-odbcConnect("RPM")
results<-sqlQuery(sqlconn,sqlString)
library(qcc)
tph <- qcc(results$tphmean[1:50], type="xbar.one", ylim=c(4000,12000), std.dev=600)
close(fileconn)
close(sqlconn)

Answer 4

这就是我使用的：

# Set Filename
fileName <- 'Input File.txt'

doSub <- function(src, dest_var_name, src_pattern, dest_pattern) {
    assign(
            x       = dest_var_name
        ,   value   = gsub(
                            pattern     = src_pattern
                        ,   replacement = dest_pattern
                        ,   x = src
                    )
        ,   envir   = .GlobalEnv
    )
}


# Read File Contents
original_text <- readChar(fileName, file.info(fileName)$size)

# Convert to UNIX line ending for ease of use
doSub(src = original_text, dest_var_name = 'unix_text', src_pattern = '\r\n', dest_pattern = '\n')

# Remove Block Comments
doSub(src = unix_text, dest_var_name = 'wo_bc_text', src_pattern = '/\\*.*?\\*/', dest_pattern = '')

# Remove Line Comments
doSub(src = wo_bc_text, dest_var_name = 'wo_bc_lc_text', src_pattern = '--.*?\n', dest_pattern = '')

# Remove Line Endings to get Flat Text
doSub(src = wo_bc_lc_text, dest_var_name = 'flat_text', src_pattern = '\n', dest_pattern = ' ')

# Remove Contiguous Spaces
doSub(src = flat_text, dest_var_name = 'clean_flat_text', src_pattern = ' +', dest_pattern = ' ')

Answer 5

尝试paste(sqlString, collapse=" ")

Answer 6

可以使用readChar()代替readLines()。我一直存在混合评论问题（--或/* */），这对我来说一直很好。

sql <- readChar(path.to.file, file.size(path.to.file))
query <- sqlQuery(con, sql, stringsAsFactors = TRUE)

Answer 7

我一起使用sql <- gsub("\n","",sql)和sql <- gsub("\t","",sql)。

将多行SQL查询导入单个字符串

7 个答案: