| dbSendQuery {DBI} | R Documentation |
The dbSendQuery() method only submits and synchronously executes the
SQL query to the database engine. It does not extract any
records — for that you need to use the dbFetch() method, and
then you must call dbClearResult() when you finish fetching the
records you need. For interactive use, you should almost always prefer
dbGetQuery().
dbSendQuery(conn, statement, ...)
conn |
A DBIConnection object, as returned by
|
statement |
a character string containing SQL. |
... |
Other parameters passed on to methods. |
This method is for SELECT queries only. Some backends may
support data manipulation queries through this method for compatibility
reasons. However, callers are strongly encouraged to use
dbSendStatement() for data manipulation statements.
The query is submitted to the database server and the DBMS executes it,
possibly generating vast amounts of data. Where these data live
is driver-specific: some drivers may choose to leave the output on the server
and transfer them piecemeal to R, others may transfer all the data to the
client – but not necessarily to the memory that R manages. See individual
drivers' dbSendQuery() documentation for details.
dbSendQuery() returns
an S4 object that inherits from DBIResult.
The result set can be used with dbFetch() to extract records.
Once you have finished using a result, make sure to clear it
with dbClearResult().
An error is raised when issuing a query over a closed
or invalid connection,
if the syntax of the query is invalid,
or if the query is not a non-NA string.
No warnings occur under normal conditions.
When done, the DBIResult object must be cleared with a call to
dbClearResult().
Failure to clear the result set leads to a warning
when the connection is closed.
If the backend supports only one open result set per connection,
issuing a second query invalidates an already open result set
and raises a warning.
The newly opened result set is valid
and must be cleared with dbClearResult().
For updates: dbSendStatement() and dbExecute().
Other DBIConnection generics: DBIConnection-class,
dbDataType, dbDisconnect,
dbExecute, dbExistsTable,
dbGetException, dbGetInfo,
dbGetQuery, dbIsValid,
dbListFields, dbListResults,
dbListTables, dbReadTable,
dbRemoveTable,
dbSendStatement, dbWriteTable
con <- dbConnect(RSQLite::SQLite(), ":memory:") dbWriteTable(con, "mtcars", mtcars) rs <- dbSendQuery(con, "SELECT * FROM mtcars WHERE cyl = 4;") dbFetch(rs) dbClearResult(rs) dbDisconnect(con)