I am using ROracle package to fetch records from database. I need to pass multiple values from dbGetQuery(), so that I can use them in where clause of query.
Suppose I have:
query <- "select abc from tablename where value1= (:1)
Then I can get the table data by calling
data <- dbGetQuery(connection, query, condition1 ).
I will get the data in data variable.
The problem I am facing is if I have to pass multiple values from dbGetQuery()
then how to do it.
Example:
query <- "select abc from tablename where value1= (:1) and value1=(:2)
now if I call
data <- dbGetQuery(connection, query, condition1, condition2)
it will give error.
I tried passing a vector but still i am getting error, like
data <- dbGetQuery(connection, query, c("condition1", "condition2"))
Is there a way I can do it?
Something like this should work:
data <- dbGetQuery(connection, query,
list=as.list(c("condition1", "condition2")))
Hope it helps.
Related
I am working with the R programming language.
Normally, when I want to get the summary of a table, I can use something like the "str()" function or the "summary()" function:
str(my_table)
summary(my_table)
However, now I am trying to do this with tables on a server.
For instance, I am trying to get the summaries of variable types for a specific table (e.g. "my_table") on a server. I found a very indirect way to do this:
#load libraries
library(OBDC)
library(RODBC)
library(dbi)
#establish a connection and name it as "dbhandle"
rs <- dbSendQuery(dbhandle, 'select * from my_table limit 1')
dbColumnInfo(rs)
My Question: Is there a more "direct" way to do this? For example, can I get information about each column (e.g. whether the column is integer, character, date, etc.) in a table without first sending the query and then requesting the information? Can I do this directly?
Thanks!
You could try using fetch() from "RMySQL" to turn your SQL query into an R object (e.g. data frame)
library(RMySQL)
rs <- dbSendQuery(dbhandle, 'select * from my_table limit 1')
# Get the results from MySQL into R
my_table = fetch(rs, n=-1)
# clear result
dbClearResult(rs)
rm(rs)
Then use the functions you describe.
str(my_table)
summary(my_table)
I want to get all rows in my database where a condition with regular expressions is met. The variable should start with "J12", "J13", "J14" or "J15".
This was my attempt:
Data <- dbGetQuery(db,
"SELECT * FROM 'XXX.XXXX.XXX'
WHERE TYPE = 'xyz' AND [xyz_DIAG] LIKE '^J1[2-5]' ")
Then a data.frame with 0 rows is returned.
When I send the query
Data <- dbGetQuery(db,
"SELECT * FROM 'XXX.XXXX.XXX'
WHERE TYPE = 'xyz'")
I get a quite large data.frame and then I call
Data %>% setDT %>% .[str_detect(xyz_DIAG, "^J1[2-5]")] and I get the expected result because in fact there are many rows that fulfill that regexp. Have I done something wrong?
For the time being, REGEXP operator has not been added to RSQLITE, see this pull request.
You thus need to "unwrap" the regex and use ORed LIKE:
Data <- dbGetQuery(db,
"SELECT * FROM 'XXX.XXXX.XXX'
WHERE TYPE = 'xyz' AND ([xyz_DIAG] LIKE 'J12%' OR [xyz_DIAG] LIKE 'J13%' OR [xyz_DIAG] LIKE 'J14%' OR [xyz_DIAG] LIKE 'J15%') ")
I am wondering what approach should have been selected to perform action from title. I am using ODBC connection and what I get from first sql query are like 40-50 rows in one column. What I want is to put this output as a values in to search for.
How should i treat this? Like a array or separated variables? I still do not know R well so just need to know where to search for.
Regards
------more explanation below----
I have list of 40-50 numbers of 10 digits each, organized in a column.
I am trying to do this:
list <- c(my_input)
sql_in <- paste0(list, collapse="")
and characters are organized like this after this operations:
'c(1234567890, , 1234567890, 1234567890)'
and almost all looks fine and fit into my query besides additional c character at the beginning and missing apostrophes.I try to use gsub function but did not work in way I want.
You may likely do this in one SQL call using a subquery. Notice in the call below that the result of
SELECT n_gear
FROM Gear
WHERE n_gear IN (3,4)
Is passed to the WHERE clause of the primary query. This is perfectly valid and will allow your query to execute entirely in SQL without having to do any intermediate steps in R.
(I use sqldf for simplicity of illustration, but this should work through just about any ODBC connection)
library(sqldf)
Gear <- data.frame(n_gear = 1:5)
sqldf(
"SELECT mpg, qsec, gear, wt
FROM mtcars
WHERE gear IN (SELECT n_gear
FROM Gear
WHERE n_gear IN (3,4))"
)
Try something like this:
list<-c("try","this") #The output from your first query
sql_in<-paste0(list, collapse="','")
The Output
paste("select * from table where table.var in ",paste("('",sql_in,"')",sep=''))
[1] "select * from table where table.var in ('try','this')"
If yuo have space as first or last element of the string you can use this code:
`list<-c(" first element is a space","try","this","last element is a space ")` #The output from your first query
Find space at first or last character
first_space<-substr(list, start = 1, stop = 1)==" "
last_space<-substr(list, start = nchar(list), stop = nchar(list))==" "
Remove spaces
list[first_space]<-substr(list[first_space], start = 2, stop = nchar(list[first_space]))
list[last_space]<-substr(list[last_space], start = 1, stop = nchar(list[last_space])-1)
sql_in<-paste0(list, collapse="','")
Your output
paste0("select * from table where table.var in ",paste("('",sql_in,"')",sep=''))
"select * from table where table.var in ('first element is a space','try','this','last element is a space')"
I think You are expecting some thing like shown below code,
data <- dbGetQuery(con, "select column from yourfirsttable")
list <- paste(data$column, collapse="','")
result <- dbGetQuery(con, statement = sprintf("select * from yourresulttable where inv in ('%s')",list))
It's not entirely clear exactly what you're wanting to achieve here. For example, one use case just means you can do it all with a join. But I have cases where I don't know the values for the test without doing some computation. Then I do a separate query having created a query string thus:
> id <- 1:5
> paste0("SELECT * FROM table WHERE ID IN (", paste0(id, collapse = ","), ")")
[1] "SELECT * FROM table WHERE ID IN (1,2,3,4,5)"
How do I bind a variable to a SQL set for an IN query in Perl DBI?
Example:
my #nature = ('TYPE1','TYPE2'); # This is normally populated from elsewhere
my $qh = $dbh->prepare(
"SELECT count(ref_no) FROM fm_fault WHERE nature IN ?"
) || die("Failed to prepare query: $DBI::errstr");
# Using the array here only takes the first entry in this example, using a array ref gives no result
# bind_param and named bind variables gives similar results
$qh->execute(#nature) || die("Failed to execute query: $DBI::errstr");
print $qh->fetchrow_array();
The result for the code as above results in only the count for TYPE1, while the required output is the sum of the count for TYPE1 and TYPE2. Replacing the bind entry with a reference to #nature (\#nature), results in 0 results.
The main use-case for this is to allow a user to check multiple options using something like a checkbox group and it is to return all the results. A work-around is to construct a string to insert into the query - it works, however it needs a whole lot of filtering to avoid SQL injection issues and it is ugly...
In my case, the database is Oracle, ideally I want a generic solution that isn't affected by the database.
There should be as many ? placeholders as there is elements in #nature, ie. in (?,?,..)
my #nature = ('TYPE1','TYPE2');
my $pholders = join ",", ("?") x #nature;
my $qh = $dbh->prepare(
"SELECT count(ref_no) FROM fm_fault WHERE nature IN ($pholders)"
) or die("Failed to prepare query: $DBI::errstr");
I have a Shiny app that has a checkbox group input. The user can select multiple inputs. I also have an ODBC connection linked to a database. The process would be that when a user selects items from the check box group, that user input would be part of a string in the sql query to filter the data.
UI.R (partial to show example)
checkboxGroupInput('Type', 'Type', c(
"AX"="AX",
"AY"="AY",
"AZ"="AZ",
"BGB"="BGB",
"BT"="BT",
"BX"="BX",
"BXT"="BXT",
"C"="C",
"CNT"="CNT")),
The column in the table where the "Type" information is in is called COMPONENT, so my sql query using RODBC is
data <- odbcConnect("database", uid="username", pwd="password")
query <- (SELECT ID, NAME, TYPE FROM COMPONENT WHERE TYPE LIKE Input$Type)
df <- odbcQuery(data, query)
The query line would not work, but I have no idea how to take multiple inputs and place them properly in the query. Also, there is an added level of complexity that I am not sure how to handle. The data in the database is alpha numeric, so instead of AX, it might be listed as AX14 or AX 71. Also, because there are some one letter types, using a wildcard seems a little difficult.
To answer your initial question regarding "multiple inputs in the query", I use concatenation to achieve this.
Using paste0(), I write something as follows:
type = "AX14"
myQuery <- paste0("Select variable1, variable2 from my_table where type like ",type)
myQuery
[1] "Select variable1, variable2 from my_table where type like AX14"
You can add little things like single quotes or wildcard operators as follows:
myQuery <- paste0("Select variable1, variable2 from my_table where type like '%",type,"%'")
myQuery
[1] "Select variable1, variable2 from my_table where type like '%AX14%'"
Then proceed with actually running the query:
df <- odbcQuery(data, myQuery)