在通过 ODBC 连接到数据库的 R 中，如何在运行一个查询后断开连接以发送另一个查询而不取消前一个查询？

Question

我是 R 的新手，也是 Stack Overflow 的新手，如果我 post 不正确，我深表歉意！我使用 ODBC 和 DBI 包将 R 链接到 Access 数据库。我搜索了互联网，但找不到编写更新查询的方法，因此我创建了一个循环，该循环几乎可以手动执行相同的操作。问题是要做到这一点，我正在使用 dbSendStatement 函数。似乎当您使用该函数时，您需要一种方法在移动到另一个查询之前结束它，否则您会收到此错误：

In new_result(connection@ptr, statement, immediate) :
  Cancelling previous query

如何完成一个查询，以便在不取消最后一个查询的情况下继续下一个查询？

这是我认为相关的代码部分：

require(DBI)
require (odbc)

dB.Connection = dbConnect(odbc::odbc(), dsn = "Development Database")

BLDG.LVL.Details = data.frame()

for (i in 2:length(Temp.File.List)){
  Temp.BLDG.LVL = read_excel(Temp.File.List[i], range = cell_cols("A:O"))
  BLDG.LVL.Details = rbind(BLDG.LVL.Details, Temp.BLDG.LVL)
  file.move(Temp.File.List[i],paste("C:/UserData/",Sys.getenv("USERNAME"),"/OneDrive - Siemens AG/Development Database/06 FIM (BLDG LVL)/Archive", sep = ""))}

for (i in 1:nrow(BLDG.LVL.Details)){
  DBI::dbSendStatement(conn = dB.Connection, statement = paste("UPDATE DC_FIMs_BLDG_Lvl SET Included = ",BLDG.LVL.Details[i,3]," WHERE FIM_ID = ",BLDG.LVL.Details[i,1]," AND BUILDING_ID = ",BLDG.LVL.Details[i,2],";", sep = ""))
  DBI::dbSendStatement(conn = dB.Connection, statement = paste("UPDATE DC_FIMs_BLDG_Lvl SET Proposed_kW_Yr1 = ",BLDG.LVL.Details[i,4]," WHERE FIM_ID = ",BLDG.LVL.Details[i,1]," AND BUILDING_ID = ",BLDG.LVL.Details[i,2],";", sep = ""))
  DBI::dbSendStatement(conn = dB.Connection, statement = paste("UPDATE DC_FIMs_BLDG_Lvl SET Proposed_kWh_Yr1 = ",BLDG.LVL.Details[i,6]," WHERE FIM_ID = ",BLDG.LVL.Details[i,1]," AND BUILDING_ID = ",BLDG.LVL.Details[i,2],";", sep = ""))
  DBI::dbSendStatement(conn = dB.Connection, statement = paste("UPDATE DC_FIMs_BLDG_Lvl SET Proposed_NGas_Yr1 = ",BLDG.LVL.Details[i,7]," WHERE FIM_ID = ",BLDG.LVL.Details[i,1]," AND BUILDING_ID = ",BLDG.LVL.Details[i,2],";", sep = ""))
  DBI::dbSendStatement(conn = dB.Connection, statement = paste("UPDATE DC_FIMs_BLDG_Lvl SET Proposed_H2O_Yr1 = ",BLDG.LVL.Details[i,8]," WHERE FIM_ID = ",BLDG.LVL.Details[i,1]," AND BUILDING_ID = ",BLDG.LVL.Details[i,2],";", sep = ""))
  DBI::dbSendStatement(conn = dB.Connection, statement = paste("UPDATE DC_FIMs_BLDG_Lvl SET Proposed_FuelOil_Yr1 = ",BLDG.LVL.Details[i,9]," WHERE FIM_ID = ",BLDG.LVL.Details[i,1]," AND BUILDING_ID = ",BLDG.LVL.Details[i,2],";", sep = ""))
  DBI::dbSendStatement(conn = dB.Connection, statement = paste("UPDATE DC_FIMs_BLDG_Lvl SET Proposed_Propane_Yr1 = ",BLDG.LVL.Details[i,10]," WHERE FIM_ID = ",BLDG.LVL.Details[i,1]," AND BUILDING_ID = ",BLDG.LVL.Details[i,2],";", sep = ""))
  DBI::dbSendStatement(conn = dB.Connection, statement = paste("UPDATE DC_FIMs_BLDG_Lvl SET Proposed_Other_Yr1 = ",BLDG.LVL.Details[i,11]," WHERE FIM_ID = ",BLDG.LVL.Details[i,1]," AND BUILDING_ID = ",BLDG.LVL.Details[i,2],";", sep = ""))
  DBI::dbSendStatement(conn = dB.Connection, statement = paste("UPDATE DC_FIMs_BLDG_Lvl SET Operational_Savings_USD_BLDG = ",BLDG.LVL.Details[i,13]," WHERE FIM_ID = ",BLDG.LVL.Details[i,1]," AND BUILDING_ID = ",BLDG.LVL.Details[i,2],";", sep = ""))
  DBI::dbSendStatement(conn = dB.Connection, statement = paste("UPDATE DC_FIMs_BLDG_Lvl SET Operational_Savings_Yrs_BLDG = ",BLDG.LVL.Details[i,14]," WHERE FIM_ID = ",BLDG.LVL.Details[i,1]," AND BUILDING_ID = ",BLDG.LVL.Details[i,2],";", sep = ""))
  DBI::dbSendStatement(conn = dB.Connection, statement = paste("UPDATE DC_FIMs_BLDG_Lvl SET Operational_Savings_Persistence_BLDG = ",BLDG.LVL.Details[i,15]," WHERE FIM_ID = ",BLDG.LVL.Details[i,1]," AND BUILDING_ID = ",BLDG.LVL.Details[i,2],";", sep = ""))
  DBI::dbSendStatement(conn = dB.Connection, statement = paste("UPDATE DC_FIMs_BLDG_Lvl SET Included = ",BLDG.LVL.Details[i,3]," WHERE FIM_ID = ",BLDG.LVL.Details[i,1]," AND BUILDING_ID = ",BLDG.LVL.Details[i,2],";", sep = ""))}

Answer 1

dbSendStatement() returns一个结果对象，需要用dbClearResult()清除。使用 dbExecute() 发送查询更容易，基本上这是 dbSendStatement() 和 dbClearResult().

的组合

for (i in 1:nrow(BLDG.LVL.Details)){
  DBI::dbExecute(conn = dB.Connection, statement = paste("UPDATE DC_FIMs_BLDG_Lvl SET Included = ",BLDG.LVL.Details[i,3]," WHERE FIM_ID = ",BLDG.LVL.Details[i,1]," AND BUILDING_ID = ",BLDG.LVL.Details[i,2],";", sep = ""))
  DBI::dbExecute(conn = dB.Connection, statement = paste("UPDATE DC_FIMs_BLDG_Lvl SET Proposed_kW_Yr1 = ",BLDG.LVL.Details[i,4]," WHERE FIM_ID = ",BLDG.LVL.Details[i,1]," AND BUILDING_ID = ",BLDG.LVL.Details[i,2],";", sep = ""))

有几种方法可以改善这一点：

使用dbQuoteLiteral()引用字面值，防止SQL注入，这也解决了In R connected to an Access Database through ODBC, how can I update a text field?:

for (i in 1:nrow(BLDG.LVL.Details)){
  DBI::dbExecute(conn = dB.Connection, statement = paste("UPDATE DC_FIMs_BLDG_Lvl SET Included = ",DBI::dbQuoteLiteral(conn,BLDG.LVL.Details[i,3])," WHERE FIM_ID = ",DBI::dbQuoteLiteral(conn,BLDG.LVL.Details[i,1])," AND BUILDING_ID = ",DBI::dbQuoteLiteral(conn,BLDG.LVL.Details[i,2]),";", sep = ""))
  DBI::dbExecute(conn = dB.Connection, statement = paste("UPDATE DC_FIMs_BLDG_Lvl SET Proposed_kW_Yr1 = ",DBI::dbQuoteLiteral(conn,BLDG.LVL.Details[i,4])," WHERE FIM_ID = ",DBI::dbQuoteLiteral(conn,BLDG.LVL.Details[i,1])," AND BUILDING_ID = ",DBI::dbQuoteLiteral(conn,BLDG.LVL.Details[i,2]),";", sep = ""))

使用参数安全地传递查询参数（遗憾的是，占位符语法因 DBMS 而异，? 可能会起作用）：

for (i in 1:nrow(BLDG.LVL.Details)){
  DBI::dbExecute(conn = dB.Connection, statement = "UPDATE DC_FIMs_BLDG_Lvl SET Included = ? WHERE FIM_ID = ? AND BUILDING_ID = ?;", params = list(BLDG.LVL.Details[i,3],BLDG.LVL.Details[i,1],BLDG.LVL.Details[i,2]))
  ...

冒着明显的风险，在同一查询中更新多个列会快得多，有或没有占位符：

for (i in 1:nrow(BLDG.LVL.Details)){
  DBI::dbExecute(conn = dB.Connection, statement = "UPDATE DC_FIMs_BLDG_Lvl SET Included = ?, Proposed_kW_Yr1 = ? WHERE FIM_ID = ? AND BUILDING_ID = ?;", params = list(BLDG.LVL.Details[i,3],BLDG.LVL.Details[i,4],BLDG.LVL.Details[i,1],BLDG.LVL.Details[i,2]))
  ...

我相信您可以用以下形式替换整个循环：
```
library(dm)

...

tbl <- dplyr::tbl(conn, "DC_FIMs_BLDG_Lvl")
dplyr::rows_update(tbl, BLDG.LVL.Details, by = c("FIM_ID", "BUILDING_ID"), in_place = TRUE, copy = TRUE)
```
该功能需要加载 dm 包。在 https://krlmlr.github.io/dm/articles/howto-dm-rows.html 阅读更多内容——该文本显示了一种不同的方法，如果您正在访问数据库中的多个表，该方法很有用。让我知道它是否适合你。
看看 dbx package 发送更新查询，它对你有用吗？

在通过 ODBC 连接到数据库的 R 中，如何在运行一个查询后断开连接以发送另一个查询而不取消前一个查询？

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