r - R sqlite:使用两个表进行更新会给出语法错误“near”。”:

Question

我想用sqlite上的两个表进行UPDATE。

x1 <- data.frame(id = rep(1,3),
                  t = as.Date(c("2000-01-01","2000-01-15","2000-01-31"))
)
x1.h <- 0
x2 <- data.frame(id = 1, start = as.Date("2000-01-14"))

UPDATE是：

sqldf(paste("UPDATE x1"
        ," SET x1.h = 1"
        ," WHERE EXISTS (SELECT *"
        ,"               FROM x2"
        ,"               WHERE x1.id = x2.id"
        ,"                     AND x1.t < x2.start"
        ,"               )"
        )
  )

我收到以下错误：

Error in sqliteExecStatement(con, statement, bind.data) : 
   RS-DBI driver: (error in statement: near ".": syntax error)

有人知道出什么问题了吗？
感谢您的帮助。

Answer 1

您为什么使用sqldf更新？我认为sqldf对于select语句而言是唯一的选择。

我会为此使用RSQLite。

首先，我更正了您的sql状态。我更喜欢使用sep'\ n'，与cat获得漂亮的请求

str.update <- paste(" UPDATE x1"
            ," SET h = 1 "              ## here the error
            ," WHERE EXISTS (SELECT * "
             ,"              FROM x2 "             ## here second error 
             ,"              WHERE x1.id = x2.id "
            ,"               AND x1.t < x2.start "
            ,"       )"
      ,sep ='\n'
)


cat(str.update)
 UPDATE x1
 SET h = 1 
 WHERE EXISTS (SELECT * 
              FROM x1,x2    ##
              WHERE x1.id = x2.id 
               AND x1.t < x2.start 
       )

然后，您可以执行以下操作：

library(RSQLite)
con <- dbConnect(SQLite(), ":memory:")
dbWriteTable(con, "x1", x1)            # I create my table x1
dbWriteTable(con, "x2", x2)            # I create my table x2
res <- dbSendQuery(con, str.update)   
dbReadTable(con,name='x1')            ## to see the result

编辑

我在Op澄清后编辑答案（ FROM x1,x2变为 FROM x2）