sql temporary tables in rstudio notebook's sql chunks? - sql

Question

I am trying to use temp tables in an sql codechunk in rstudio.
An example: When I select one table and return it into an r object things seem to be working:
```{sql , output.var="x", connection='db' }
SELECT count(*) n
FROM origindb
```
When I try anything with temp tables it seems like the commands are running but returns an empty r data.frame
```{sql , output.var="x", connection='db' }
SELECT count(*) n
INTO #whatever
FROM origindb
SELECT *
FROM #whatever
```
My impression is that the Rstudio notebook sql chunks are just set to make one single query. So my temporary solution is to create the tables in a stored procedure in the database. Then I can get the results I want with something simple. I would prefer to have a bit more flexibility in the sql code chunks.
my db connection looks like this:
```{r,echo=F}
db <- DBI::dbConnect(odbc::odbc(),
driver = "SQL Server",
server = 'sql',
database = 'databasename')
```

Answer 1

Like this question, it will work if you put
set nocount on
at the top of your chunk. R seems to get confused when it's handed back the rowcount for the temp table.

Answer 2

I accomplished my goal using CTEs. As long as you define your CTEs in the order that they will be used it works. It is just like using temp tables with one big exception. The CTEs are gone after the query finishes where temp tables exist until you spid is kill (typically via a disconnect).
WITH CTE_WHATEVER AS (
SELECT COUNT(*) n
FROM origindb
)
SELECT *
FROM CTE_WHATEVER
You can also do this for multiple temp table examples
WITH CTE1 AS (
SELECT
STATE
,COUNTY
,COUNT(*) n
FROM origindb
GROUP BY
STATE
,COUNTY
),
CTE2 AS (
SELECT
STATE
,AVG(n)
,COUNTY_AVG
FROM CTE1
GROUP BY
STATE
)
SELECT *
FROM CTE2
WHERE COUNTY_AVG > 1000000
Sorry for the formatting. I couldn't figure out how to get the carriage returns to work in the code block.
I hope this helps.

Answer 3

You could manage a transaction within the SQL chunk defining a BEGIN and COMMIT clauses. For example:
BEGIN ;
CREATE TABLE foo (id varchar) ;
COMMENT ON TABLE foo IS 'Foo';
COMMIT ;