我正在使用RSQLite访问简单的SQLite数据库以返回定义的数据集。我希望能够限制查询，以便通过限制类别字段仅返回数据的子集。
我编写了一个函数，希望能够提供在where子句中使用的参数，但是当我以值作为参数运行该函数时，我不断收到“对象'AAPL'发现错误” （其中参数为AAPL）。
通过硬编码要在函数中限制的值，它可以正常工作，运行f2(5)将返回'AAPL'的前5行
f2 <- function(n, stockName) {
library(RSQLite)
conSQLiteParallel <- dbConnect("SQLite", dbname="stocks.sqlite")
## this sql works fine
sqlcmdParallel <- paste("SELECT stock, gain ",
"FROM stock_gains ",
"WHERE day <=", n, " and stock ='AAPL'", sep="")
resultsHandleParallel <- dbSendQuery(conSQLiteParallel, sqlcmdParallel)
d <- fetch(resultsHandleParallel)
}
results <- f2(5)
但是，当我尝试使用stockName变量将值传递给函数时，它给了我
f2 <- function(n, stockName) {
library(RSQLite)
conSQLiteParallel <- dbConnect("SQLite", dbname="stocks.sqlite")
## this sql does not work correctly, but only gives an error
## when running the function
sqlcmdParallel <- paste("SELECT stock, gain ",
"FROM stock_gains ",
"WHERE stock =", stockName, sep="")
resultsHandleParallel <- dbSendQuery(conSQLiteParallel, sqlcmdParallel)
d <- fetch(resultsHandleParallel)
}
results <- f2(5,APPL) - gives the error "Error in paste("SELECT stock, gain FROM stock_gains WHERE stock =", stockName, :
object 'APPL' not found"
results <- f2(5,'APPL') - gives the error "Error in sqliteExecStatement(conn, statement, ...) :
RS-DBI driver: (error in statement: no such column: APPL) "
results <- f2(5,distinctStocks[1,1]) - gives the error "Error in sqliteExecStatement(conn, statement, ...) :
RS-DBI driver: (error in statement: no such column: AAPL) "
如有任何帮助，我们将不胜感激，不胜感激。
最佳答案
stockName应该用引号引起来：
paste0("SELECT stock, gain FROM stock_gains WHERE day <= ", n,
" and stock = '", stockName, "'")
这也应该起作用：
library(gsubfn)
fn$identity("SELECT stock, gain
FROM stock_gains
WHERE day <= $n and stock = '$stockName'")
关于r - 使用RSQLite的R中分类变量的where子句，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/23848833/