sqldf 中的 R sprintf 就像 [英] R sprintf in sqldf's like

问题描述

我想在 R 中使用 sqldf 进行循环查询，以选择日期为11/12/2015"和上午 9 点的所有非 NULL X.1 变量.示例:

I would like to do a looping query in R using sqldf to that select all non-NULL X.1 variable with date "11/12/2015" and at 9AM. Example :

StartDate              X.1
11/12/2015 09:14        A
11/12/2015 09:36        
11/12/2015 09:54        A

日期在其他查询生成的变量中

The date is in variable that generated from other query

nullob<-0
dayminnull<-as.numeric(sqldf("SELECT substr(Min(StartDate),1,03)as hari     from testes")) # this produce "11/12/2015"
  for (i in 1 : 12){
    dday<-mdy(dayminnull)+days(i) #go to next day
    sqlsql <- sprintf("SELECT count([X.1]) FROM testes where StartDate like '% \%s 09: %'", dday)
    x[i]<-sqldf(sqlsql)
    nullob<-nullob+x[i]
}

它带有错误:Error in sprintf("SELECT count([X.1]) FROM testes WHERE StartDate like '%%s 09%'", :无法识别的格式规范%"拜托了.提前谢谢你

And it comes with error : Error in sprintf("SELECT count([X.1]) FROM testes WHERE StartDate like '%%s 09%'", : unrecognised format specification '%' Please hellp. thank you in advance

推荐答案

在文档中不是 super 清楚的，而是一个 % 后跟一个 %，即 %%，是告诉 sprintf 使用文字 % 的方式.我们可以很容易地对此进行测试:

It's not super clear in the documentation, but a % followed by a %, that is %%, is the way to tell sprintf to use a literal %. We can test this fairly easily:

sprintf("%% %s %%", "hi")
[1] "% hi %" 

对于您的查询字符串，这应该有效:

For your query string, this should work:

sprintf("SELECT count([X.1]) FROM testes where StartDate like '%% %s 09: %%'", dday)

<小时>

来自?sprintf:

字符串 fmt 包含普通字符，这些字符被传递到输出字符串，以及操作的转换规范通过 ... 提供的参数.允许的转换规范以 % 开头，以设置 aAdifeEgGosxX%.这些字母表示以下类型:

The string fmt contains normal characters, which are passed through to the output string, and also conversion specifications which operate on the arguments provided through .... The allowed conversion specifications start with a % and end with one of the letters in the set aAdifeEgGosxX%. These letters denote the following types:

... [关于aAdifeEgGosxX的文档]

... [Documentation on aAdifeEgGosxX]

• %:文字 %(在这种情况下，不允许使用下面给出的任何额外格式字符).

• %: Literal % (none of the extra formatting characters given below are permitted in this case).

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