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Data Loading ​

SQL data loading utilities. These methods generate queries that load data into DuckDB.

loadExtension ​

loadExtension(extensionName)

Generates a query to install and load a named DuckDB extension. For example, vg.loadExtension("spatial") will load the spatial extension.

loadCSV ​

loadCSV(tableName, file, options)

Generate a SQL query to create a table containing the values of a CSV file. The file argument may be a URL or a local filesystem path (if running DuckDB locally, not via WebAssembly).

The supported options are:

  • select: An optional list of column expressions to select. If not specified, all columns are included.
  • where: An optional filter predicate (WHERE clause) to filter the data on load.
  • view: A boolean flag (default false) indicating if a VIEW should be created over the file, rather than a TABLE.
  • temp: A boolean flag (default true) indicating if the created table or view should be a temporary instance that should not persist beyond the current session.
  • replace: A boolean flag (default false) indicating that the file contents should replace any existing table or view with the same name. The default behavior is to do nothing if a name conflict exists.
  • Additional CSV-specific options, see the DuckDB CSV documentation.
js
// Loads file.csv into the table "table1" with default options:
// CREATE TEMP TABLE IF NOT EXISTS table1 AS
//   SELECT *
//   FROM read_csv('file.csv', auto_detect=true, sample_size=-1)
loadCSV("table1", "file.csv");

loadJSON ​

loadJSON(tableName, file, options)

Generate a SQL query to create a table containing the values of a JSON file. The file argument may be a URL or a local filesystem path (if running DuckDB locally, not via WebAssembly).

The supported options are:

  • select: An optional list of column expressions to select. If not specified, all columns are included.
  • where: An optional filter predicate (WHERE clause) to filter the data on load.
  • view: A boolean flag (default false) indicating if a VIEW should be created over the file, rather than a TABLE.
  • temp: A boolean flag (default true) indicating if the created table or view should be a temporary instance that should not persist beyond the current session.
  • replace: A boolean flag (default false) indicating that the file contents should replace any existing table or view with the same name. The default behavior is to do nothing if a name conflict exists.
  • Additional JSON-specific options. See the DuckDB JSON documentation.
js
// Loads file.json into the table "table1" with default options:
// CREATE TEMP TABLE IF NOT EXISTS table1 AS
//   SELECT *
//   FROM read_json('file.json', auto_detect=true, json_format='auto')
loadJSON("table1", "file.json");

loadParquet ​

loadParquet(tableName, file, options)

Generate a SQL query to create a table containing the values of a Parquet file. The file argument may be a URL or a local filesystem path (if running DuckDB locally, not via WebAssembly).

The supported options are:

  • select: An optional list of column expressions to select. If not specified, all columns are included.
  • where: An optional filter predicate (WHERE clause) to filter the data on load.
  • view: A boolean flag (default false) indicating if a VIEW should be created over the file, rather than a TABLE.
  • temp: A boolean flag (default true) indicating if the created table or view should be a temporary instance that should not persist beyond the current session.
  • replace: A boolean flag (default false) indicating that the file contents should replace any existing table or view with the same name. The default behavior is to do nothing if a name conflict exists.
  • Additional Parquet-specific options. See the DuckDB Parquet documentation.
js
// Load named columns from a parquet file, filtered upon load:
// CREATE TEMP TABLE IF NOT EXISTS table1 AS
//   SELECT foo, bar, value
//   FROM read_parquet('file.parquet')
//   WHERE value > 1
loadParquet("table1", "file.parquet", {
  select: [ "foo", "bar", "value" ],
  where: "value > 1"
});

loadObjects ​

loadObjects(tableName, objects, options)

Generate a SQL query to create a table containing the values of the provided JavaScript objects.

The supported options are:

  • select: An optional list of column expressions to select. If not specified, all columns are included.
  • view: A boolean flag (default false) indicating if a VIEW should be created over the file, rather than a TABLE.
  • temp: A boolean flag (default true) indicating if the created table or view should be a temporary instance that should not persist beyond the current session.
  • replace: A boolean flag (default false) indicating that the file contents should replace any existing table or view with the same name. The default behavior is to do nothing if a name conflict exists.
js
// CREATE TEMP TABLE IF NOT EXISTS table3 AS
//   (SELECT 1 AS "foo", 2 AS "bar") UNION ALL
//   (SELECT 3 AS "foo", 4 AS "bar") UNION ALL ...
const q = loadObjects("table3", [
  { foo: 1, bar: 2 },
  { foo: 3, bar: 4 },
  ...
]);

loadSpatial ​

loadSpatial(tableName, file, options)

Generate a SQL query to create a table containing the values of a spatial data file by calling the ST_Read function of the DuckDB spatial extension. The file argument may be a URL or a local filesystem path (if running DuckDB locally, not via WebAssembly).

The supported options are:

  • select: An optional list of column expressions to select. If not specified, all columns are included.
  • where: An optional filter predicate (WHERE clause) to filter the data on load.
  • view: A boolean flag (default false) indicating if a VIEW should be created over the file, rather than a TABLE.
  • temp: A boolean flag (default true) indicating if the created table or view should be a temporary instance that should not persist beyond the current session.
  • replace: A boolean flag (default false) indicating that the file contents should replace any existing table or view with the same name. The default behavior is to do nothing if a name conflict exists.
  • layer: The layer to extract from a multi-layer file. For example, for TopoJSON data this indicates which named object to extract.
  • Additional spatial-specific options. See the DuckDB spatial documentation.
js
// Loads us-states.json into the table "table1":
// CREATE TEMP TABLE IF NOT EXISTS table1 AS
//   SELECT *
//   FROM st_read('us-states.json', layer="states")
loadSpatial("table1", "us-states.json", "states");