Read and write MariaDB tables.

These methods read or write entire tables from a MariaDB database.

# S4 method for MariaDBConnection
dbAppendTable(conn, name, value, ..., row.names = NULL)

# S4 method for MariaDBConnection,character
dbExistsTable(conn, name, ...)

# S4 method for MariaDBConnection
dbListObjects(conn, prefix = NULL, ...)

# S4 method for MariaDBConnection
dbListTables(conn, ...)

# S4 method for MariaDBConnection,character
dbReadTable(conn, name, ..., row.names = FALSE, check.names = TRUE)

# S4 method for MariaDBConnection,character
dbRemoveTable(conn, name, ..., temporary = FALSE, fail_if_missing = TRUE)

# S4 method for MariaDBConnection,character,character
dbWriteTable(
  conn,
  name,
  value,
  field.types = NULL,
  overwrite = FALSE,
  append = FALSE,
  header = TRUE,
  row.names = FALSE,
  nrows = 50,
  sep = ",",
  eol = "\n",
  skip = 0,
  quote = "\"",
  temporary = FALSE,
  ...
)

# S4 method for MariaDBConnection,character,data.frame
dbWriteTable(
  conn,
  name,
  value,
  field.types = NULL,
  row.names = FALSE,
  overwrite = FALSE,
  append = FALSE,
  ...,
  temporary = FALSE
)

Arguments

conn

a MariaDBConnection object, produced by DBI::dbConnect()

name

a character string specifying a table name.

value

A data frame.

...

Unused, needed for compatibility with generic.

row.names

Either TRUE, FALSE, NA or a string.

If TRUE, always translate row names to a column called "row_names". If FALSE, never translate row names. If NA, translate rownames only if they're a character vector.

A string is equivalent to TRUE, but allows you to override the default name.

For backward compatibility, NULL is equivalent to FALSE.

prefix

A fully qualified path in the database's namespace, or NULL. This argument will be processed with dbUnquoteIdentifier(). If given the method will return all objects accessible through this prefix.

check.names

If TRUE, the default, column names will be converted to valid R identifiers.

temporary

If TRUE, creates a temporary table that expires when the connection is closed. For dbRemoveTable(), only temporary tables are considered if this argument is set to TRUE.

fail_if_missing

If FALSE, dbRemoveTable() succeeds if the table doesn't exist.

field.types

Optional, overrides default choices of field types, derived from the classes of the columns in the data frame.

overwrite

a logical specifying whether to overwrite an existing table or not. Its default is FALSE.

append

a logical specifying whether to append to an existing table in the DBMS. If appending, then the table (or temporary table) must exist, otherwise an error is reported. Its default is FALSE.

header

logical, does the input file have a header line? Default is the same heuristic used by read.table(), i.e., TRUE if the first line has one fewer column that the second line.

nrows

number of lines to rows to import using read.table from the input file to create the proper table definition. Default is 50.

sep

field separator character

eol

End-of-line separator

skip

number of lines to skip before reading data in the input file.

quote

the quote character used in the input file (defaults to \".)

Value

A data.frame in the case of dbReadTable(); otherwise a logical indicating whether the operation was successful.

Details

When using load_data_local_infile = TRUE in dbConnect(), pass safe = FALSE to dbAppendTable() to avoid transactions. Because LOAD DATA INFILE is used internally, this means that rows violating primary key constraints are now silently ignored.

Note

The data.frame returned by dbReadTable() only has primitive data, e.g., it does not coerce character data to factors. Temporary tables are ignored for dbExistsTable() and dbListTables() due to limitations of the underlying C API. For this reason, a prior existence check is performed only before creating a regular persistent table; an attempt to create a temporary table with an already existing name will fail with a message from the database driver.

Examples

if (mariadbHasDefault()) {
  con <- dbConnect(RMariaDB::MariaDB(), dbname = "test")

  # By default, row names are written in a column to row_names, and
  # automatically read back into the row.names()
  dbWriteTable(con, "mtcars", mtcars[1:5, ], temporary = TRUE)
  dbReadTable(con, "mtcars")
  dbReadTable(con, "mtcars", row.names = FALSE)
}
#>    mpg cyl disp  hp drat    wt  qsec vs am gear carb
#> 1 21.0   6  160 110 3.90 2.620 16.46  0  1    4    4
#> 2 21.0   6  160 110 3.90 2.875 17.02  0  1    4    4
#> 3 22.8   4  108  93 3.85 2.320 18.61  1  1    4    1
#> 4 21.4   6  258 110 3.08 3.215 19.44  1  0    3    1
#> 5 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2