dbGetRowsAffected: The number of rows affected

In DBI: R Database Interface

The number of rows affected

Description

This method returns the number of rows that were added, deleted, or updated by a data manipulation statement.

\Sexpr[results=rd,stage=render]{DBI:::methods_as_rd("dbGetRowsAffected")}

Usage

dbGetRowsAffected(res, ...)

Arguments

res	An object inheriting from DBIResult.
...	Other arguments passed on to methods.

Value

dbGetRowsAffected() returns a scalar number (integer or numeric), the number of rows affected by a data manipulation statement issued with dbSendStatement(). The value is available directly after the call and does not change after calling dbFetch(). NA_integer_ or NA_numeric_ are allowed if the number of rows affected is not known.

For queries issued with dbSendQuery(), zero is returned before and after the call to dbFetch(). NA values are not allowed.

The command execution flow

This section gives a complete overview over the flow for the execution of SQL statements that have side effects such as stored procedures, inserting or deleting data, or setting database or connection options. Most of this flow, except repeated calling of dbBindArrow(), is implemented by dbExecute(), which should be sufficient for non-parameterized queries. This flow requires an active connection established by dbConnect(). See also vignette("dbi-advanced") for a walkthrough.

1. Use dbSendStatement() to create a result set object of class DBIResult. For some queries you need to pass immediate = TRUE.

2. Optionally, bind query parameters withdbBind() or dbBindArrow(). This is required only if the query contains placeholders such as ⁠?⁠ or ⁠$1⁠, depending on the database backend.

3. Optionally, use dbGetRowsAffected() to retrieve the number of rows affected by the query.

4. Repeat the last two steps as necessary.

5. Use dbClearResult() to clean up the result set object. This step is mandatory even if no rows have been fetched or if an error has occurred during the processing. It is good practice to use on.exit() or withr::defer() to ensure that this step is always executed.

Failure modes

Attempting to get the rows affected for a result set cleared with dbClearResult() gives an error.

See Also

Other DBIResult generics: DBIResult-class, dbBind(), dbClearResult(), dbColumnInfo(), dbFetch(), dbGetInfo(), dbGetRowCount(), dbGetStatement(), dbHasCompleted(), dbIsReadOnly(), dbIsValid(), dbQuoteLiteral(), dbQuoteString()

Other command execution generics: dbBind(), dbClearResult(), dbExecute(), dbSendStatement()

Examples

con <- dbConnect(RSQLite::SQLite(), ":memory:")

dbWriteTable(con, "mtcars", mtcars)
rs <- dbSendStatement(con, "DELETE FROM mtcars")
dbGetRowsAffected(rs)
nrow(mtcars)

dbClearResult(rs)
dbDisconnect(con)

DBI documentation built on June 22, 2024, 9:41 a.m.