dbExecute: Change database state

In rstats-db/DBI: R Database Interface

Change database state

Description

Executes a statement and returns the number of rows affected. dbExecute() comes with a default implementation (which should work with most backends) that calls dbSendStatement(), then dbGetRowsAffected(), ensuring that the result is always freed by dbClearResult(). For passing query parameters, see dbBind(), in particular the "The command execution flow" section.

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

Usage

dbExecute(conn, statement, ...)

Arguments

conn	A DBIConnection object, as returned by dbConnect().
statement	a character string containing SQL.
...	Other parameters passed on to methods.

Details

You can also use dbExecute() to call a stored procedure that performs data manipulation or other actions that do not return a result set. To execute a stored procedure that returns a result set, or a data manipulation query that also returns a result set such as ⁠INSERT INTO ... RETURNING ...⁠, use dbGetQuery() instead.

Value

dbExecute() always returns a scalar numeric that specifies the number of rows affected by the statement.

Implementation notes

Subclasses should override this method only if they provide some sort of performance optimization.

Failure modes

An error is raised when issuing a statement over a closed or invalid connection, if the syntax of the statement is invalid, or if the statement is not a non-NA string.

Additional arguments

The following arguments are not part of the dbExecute() generic (to improve compatibility across backends) but are part of the DBI specification:

• params (default: NULL)

• immediate (default: NULL)

They must be provided as named arguments. See the "Specification" sections for details on their usage.

Specification

The param argument allows passing query parameters, see dbBind() for details.

Specification for the immediate argument

The immediate argument supports distinguishing between "direct" and "prepared" APIs offered by many database drivers. Passing immediate = TRUE leads to immediate execution of the query or statement, via the "direct" API (if supported by the driver). The default NULL means that the backend should choose whatever API makes the most sense for the database, and (if relevant) tries the other API if the first attempt fails. A successful second attempt should result in a message that suggests passing the correct immediate argument. Examples for possible behaviors:

1. DBI backend defaults to immediate = TRUE internally

   1. A query without parameters is passed: query is executed

   2. A query with parameters is passed:

      1. params not given: rejected immediately by the database because of a syntax error in the query, the backend tries immediate = FALSE (and gives a message)

      2. params given: query is executed using immediate = FALSE

2. DBI backend defaults to immediate = FALSE internally

   1. A query without parameters is passed:

      1. simple query: query is executed

      2. "special" query (such as setting a config options): fails, the backend tries immediate = TRUE (and gives a message)

   2. A query with parameters is passed:

      1. params not given: waiting for parameters via dbBind()

      2. params given: query is executed

See Also

For queries: dbSendQuery() and dbGetQuery().

Other DBIConnection generics: DBIConnection-class, dbAppendTable(), dbAppendTableArrow(), dbCreateTable(), dbCreateTableArrow(), dbDataType(), dbDisconnect(), dbExistsTable(), dbGetException(), dbGetInfo(), dbGetQuery(), dbGetQueryArrow(), dbIsReadOnly(), dbIsValid(), dbListFields(), dbListObjects(), dbListResults(), dbListTables(), dbQuoteIdentifier(), dbReadTable(), dbReadTableArrow(), dbRemoveTable(), dbSendQuery(), dbSendQueryArrow(), dbSendStatement(), dbUnquoteIdentifier(), dbWriteTable(), dbWriteTableArrow()

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

Examples

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

dbWriteTable(con, "cars", head(cars, 3))
dbReadTable(con, "cars")   # there are 3 rows
dbExecute(
  con,
  "INSERT INTO cars (speed, dist) VALUES (1, 1), (2, 2), (3, 3)"
)
dbReadTable(con, "cars")   # there are now 6 rows

# Pass values using the param argument:
dbExecute(
  con,
  "INSERT INTO cars (speed, dist) VALUES (?, ?)",
  params = list(4:7, 5:8)
)
dbReadTable(con, "cars")   # there are now 10 rows

dbDisconnect(con)

rstats-db/DBI documentation built on April 15, 2024, 6:51 a.m.