How to vectorize an SQL update query in R - sql

Question

I have the following zoo object (res)
column1 column2 column3
2015-12-30 3.2735 2.3984 1.1250
2015-12-31 2.5778 1.8672 1.1371
2016-01-01 3.3573 2.4999 1.1260
2016-01-04 3.3573 2.4999 1.1463
and I would like to produce a vectorized update query.
UPDATE table SET column1=3.2735, column2=2.3984, column3=1.1250 WHERE dt = '2015-12-30';
UPDATE table SET column1=2.5778, column2=1.8672, column3=1.1371 WHERE dt = '2015-12-31';
etc.
I was able to do something similar previously for an INSERT query
sColumns <- paste0("dt, index, ", paste0(colnames(res), collapse=", "))
sValues = apply(data.frame(paste0("'", index(res), "'"), paste0("'", index, "'"), coredata(res)),
1 , paste, collapse = ",")
sql <- paste0("INSERT INTO table (", sColumns, ") VALUES (", sValues, ")")
which was considerably easier because all column names were grouped, and all values were grouped. For an UPDATE query, I have to combine alternately columns and fields.
So far, I have the following:
sColumns <- paste0(colnames(res), "=")
tmp <- paste(c(matrix(c(sColumns, res[1, ]), 2, byrow = T)), collapse = ", ")
tmp <- gsub("=, ", "=", tmp)
Which produces (for one row), output like:
[1] "column1=3.2735, column2=2.3984, column3=1.125"
Can anyone provide guidance as to how I can use something like apply() to do this for all rows of 'res'?

Answer 1

1) Try this:
library(zoo)
sapply(1:nrow(res), function(i) paste0(
"UPDATE table SET ",
toString(paste0(names(res), "=", coredata(res)[i, ])),
" WHERE dt='", time(res)[i], "'"))
giving the following character vector:
[1] "UPDATE table SET column1=3.2735, column2=2.3984, column3=1.125 WHERE dt='2015-12-30'"
[2] "UPDATE table SET column1=2.5778, column2=1.8672, column3=1.1371 WHERE dt='2015-12-31'"
[3] "UPDATE table SET column1=3.3573, column2=2.4999, column3=1.126 WHERE dt='2016-01-01'"
[4] "UPDATE table SET column1=3.3573, column2=2.4999, column3=1.1463 WHERE dt='2016-01-04'"
2) And a variation giving the same result:
sapply(unname(split(res, time(res))), function(z) paste0(
"UPDATE table SET ",
toString(paste0(names(z), "=", z)),
" WHERE dt='", time(z), "'"))
Note 1: If your table is not too large then you could alternately consider reading it into R, performing the update in R and then writing it back.
Note 2: Here is the input shown reproducibly:
Lines <- "Date column1 column2 column3
2015-12-30 3.2735 2.3984 1.1250
2015-12-31 2.5778 1.8672 1.1371
2016-01-01 3.3573 2.4999 1.1260
2016-01-04 3.3573 2.4999 1.1463"
library(zoo)
res <- read.zoo(text = Lines, header = TRUE)

Answer 2

Is this what you want?
foo <- apply(res,1, function(x){
sprintf("%s = %f", names(x),x)
})
lapply(colnames(foo), function(nn) {
sprintf("UPDATE table SET %s WHERE dt = \'%s\'",
paste(foo[,nn], collapse=","),
nn)
})
which gives:
[[1]]
[1] "UPDATE table SET column1 = 3.273500,column2 = 2.398400,column3 = 1.125000 WHERE dt = '2015-12-30'"
[[2]]
[1] "UPDATE table SET column1 = 2.577800,column2 = 1.867200,column3 = 1.137100 WHERE dt = '2015-12-31'"
[[3]]
[1] "UPDATE table SET column1 = 3.357300,column2 = 2.499900,column3 = 1.126000 WHERE dt = '2016-01-01'"
[[4]]
[1] "UPDATE table SET column1 = 3.357300,column2 = 2.499900,column3 = 1.146300 WHERE dt = '2016-01-04'"