Is there a better way to code this sqlQuery in R?

Question

I'm writing an R script to get some database data and then do stuff with it, using the RODBC package. Currently all my sqlQuery commands are one long string;

stsample<-sqlQuery(odcon, paste"select * from bob.DESIGNSAMPLE T1, bob.DESIGNSUBJECTGROUP T2, bob.DESIGNEVENT T3, bob.CONFIGSAMPLETYPES T4 WHERE T1.SUBJECTGROUPID = T2.SUBJECTGROUPID AND T1.TREATMENTEVENTID = T3.TREATMENTEVENTID AND T1.SAMPLETYPEKEY = T4.SAMPLETYPEKEY AND T1.STUDYID = T2.STUDYID AND T1.STUDYID = T3.STUDYID AND T1.STUDYID = ", chstudid, sep=""))
head(stsample)

which looks ugly and is hard to read/update. I've tried putting them multiline, but then new line characters get in the way, currently my best is this using lots of paste's;

stsample<-sqlQuery(odcon,
    paste(
        "select ",
            "* ", 
        "from ", 
            "BOB.DESIGNSAMPLE T1, ",
            "BOB.DESIGNSUBJECTGROUP T2, ",
            "BOB.DESIGNEVENT T3, ",
            "BOB.CONFIGSAMPLETYPES T4 ",
        "WHERE ",
            "T1.SUBJECTGROUPID = T2.SUBJECTGROUPID ",
            "AND T1.TREATMENTEVENTID = T3.TREATMENTEVENTID ",
            "AND T1.SAMPLETYPEKEY = T4.SAMPLETYPEKEY ",
            "AND T1.STUDYID = T2.STUDYID ",
            "AND T1.STUDYID = T3.STUDYID ",
            "AND T1.STUDYID = ",chstudid,
        sep="")
    )
head(stsample)

But I don't like having to put quotes around everyline, and getting my whitespace correct. Is there a better way ?

Answer 1

I would use something like this:

stsample<-sqlQuery(odcon,
    paste("
####DATASET CONSTRUCTION QUERY #########
    select 
    *  
    from 
    BOB.DESIGNSAMPLE T1, 
    BOB.DESIGNSUBJECTGROUP T2, 
    BOB.DESIGNEVENT T3, 
    BOB.CONFIGSAMPLETYPES T4 
    WHERE 
    T1.SUBJECTGROUPID = T2.SUBJECTGROUPID 
    AND T1.TREATMENTEVENTID = T3.TREATMENTEVENTID 
    AND T1.SAMPLETYPEKEY = T4.SAMPLETYPEKEY 
    AND T1.STUDYID = T2.STUDYID 
    AND T1.STUDYID = T3.STUDYID 
    AND T1.STUDYID = 
###################################   
    ", as.character(chstudid), sep="")
    )

Answer 2

使用gsub（“\\ n”，“”，“长多行选择字符串”）而不是粘贴怎么样？

Answer 3

This is a really old question, but thought this may be useful to someone.

One thing I have found useful is the GetoptLong package, which provides the qq() function. I think it is inspired by Perl, but essentially it provides a way to do a multiline string with easy variable interpolation. For example:

library(GetoptLong)

tableName <- "myTable"
id <- 42

sqlQuery(odcon, qq("
    SELECT * FROM @{tableName}
    WHERE id = @{id}
    LIMIT 1
")

Obviously I should mention the usual caveat that this is a bad idea if you are working directly with user input and it would be better to use some kind of prepared statement in that case.