Description Usage Arguments Details Value See Also
These function retrieve the respective tables and views as a data frame from the database.
conn |
Database connection. |
start_datetime |
Start date and time as a single POSIXct value. |
end_datetime |
End date and time as a single POSIXct value. |
md_id |
Integer vector of measurand ID. |
Most of the listed function retrieve present tables in the database. For
convinience, function of the form dbReadTable_*_detail
receive the
views which join different database tables together. For example,
dbReadTable_measurand_detail
retrieves the measurand
table with
all id fields replaced by the corresponding information in
physical_quantity
, calibration_state
, etc. Only the tables that
include measurement data allow a preselection of the data to retrieve only a
part of the data set.
The functions return a data frame that contains the data from the
respective remote table, effectively the result of calling
dbGetQuery
with SELECT * FROM <name>
. Commands
that retrieve measurement data (dbReadTable_station_*
) allow a
preselection of the data with start_datetime
, end_datetime
and md_id
; all other tables are retrieved completely. An error is
raised if the table does not exist. An empty table is returned as a data
frame with zero rows.
dbReadTable
for the general function to retrieve
complete tables. dbGetQuery
and
http://db.rstudio.com/best-practices/run-queries-safely/ for more
general SQL queries. Alternatively, you can use tbl
of
the dplyr
package to only work on part of the database.
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