Welcome toVigges Developer Community-Open, Learning,Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
1.0k views
in Technique[技术] by (71.8m points)

database - Bind variables in R DBI

In R's DBI package, I'm not finding a facility for using bound variables. I did find a document (the original vignette from 2002) that says about bound variables, "Perhaps the DBI could at some point in the future implement this feature", but it looks like so far that's left undone.

What do people in R use for a substitute? Just concatenate strings right into the SQL? That's got some obvious problems for safety & performance.

EDIT:

Here's an example of how placeholders could work:

query <- "SELECT numlegs FROM animals WHERE color=?"
result <- dbGetQuery(caseinfo, query, bind="green")

That's not a very well-thought-out interface, but the idea is that you can use a value for bind and the driver handles the details of escaping (if the underlying API doesn't handle bound variables natively) without the caller having to reimplement it [badly].

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Answer

0 votes
by (71.8m points)

For anyone coming to this question like I just did after googling for rsqlite and dbgetpreparedquery, it seems that in the latest version of rsqlite you can run a SELECT query with bind variables. I just ran the following:

query <- "SELECT probe_type,next_base,color_channel FROM probes WHERE probeid=?"
probe.types.df <- dbGetPreparedQuery(con,que,bind.data=data.frame(probeids=ids))

This was relatively fast (selecting 2,000 rows out of a 450,000 row table) and is incredibly useful.

FYI.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome to Vigges Developer Community for programmer and developer-Open, Learning and Share
...