kedro.extras.datasets.pandas.SQLQueryDataSet

class kedro.extras.datasets.pandas.SQLQueryDataSet(sql, credentials, load_args=None)

SQLQueryDataSet loads data from a provided SQL query. It uses pandas.DataFrame internally, so it supports all allowed pandas options on read_sql_query. Since Pandas uses SQLAlchemy behind the scenes, when instantiating SQLQueryDataSet one needs to pass a compatible connection string either in credentials (see the example code snippet below) or in load_args. Connection string formats supported by SQLAlchemy can be found here: https://docs.sqlalchemy.org/en/13/core/engines.html#database-urls

It does not support save method so it is a read only data set. To save data to a SQL server use SQLTableDataSet.

Example:

from kedro.extras.datasets.pandas import SQLQueryDataSet
import pandas as pd

data = pd.DataFrame({"col1": [1, 2], "col2": [4, 5],
                     "col3": [5, 6]})
sql = "SELECT * FROM table_a"
credentials = {
    "con": "postgresql://scott:tiger@localhost/test"
}
data_set = SQLQueryDataSet(sql=sql,
                           credentials=credentials)

sql_data = data_set.load()

Methods

exists()	Checks whether a data set’s output already exists by calling the provided _exists() method.
from_config(name, config[, load_version, …])	Create a data set instance using the configuration provided.
load()	Loads data by delegation to the provided load method.
release()	Release any cached data.
save(data)	Saves data by delegation to the provided save method.

__init__(sql, credentials, load_args=None)

Creates a new SQLQueryDataSet.

Parameters

• sql (str) – The sql query statement.

• credentials (Dict[str, Any]) – A dictionary with a SQLAlchemy connection string. Users are supposed to provide the connection string ‘con’ through credentials. It overwrites con parameter in load_args and save_args in case it is provided. To find all supported connection string formats, see here: https://docs.sqlalchemy.org/en/13/core/engines.html#database-urls

• load_args (Optional[Dict[str, Any]]) – Provided to underlying pandas read_sql_query function along with the connection string. To find all supported arguments, see here: https://pandas.pydata.org/pandas-docs/stable/generated/pandas.read_sql_query.html To find all supported connection string formats, see here: https://docs.sqlalchemy.org/en/13/core/engines.html#database-urls

Raises

DataSetError – When either sql or con parameters is emtpy.

exists()

Checks whether a data set’s output already exists by calling the provided _exists() method.

Return type

bool

Returns

Flag indicating whether the output already exists.

Raises

DataSetError – when underlying exists method raises error.

classmethod from_config(name, config, load_version=None, save_version=None)

Create a data set instance using the configuration provided.

Parameters

• name (str) – Data set name.

• config (Dict[str, Any]) – Data set config dictionary.

• load_version (Optional[str]) – Version string to be used for load operation if the data set is versioned. Has no effect on the data set if versioning was not enabled.

• save_version (Optional[str]) – Version string to be used for save operation if the data set is versioned. Has no effect on the data set if versioning was not enabled.

Return type

AbstractDataSet

Returns

An instance of an AbstractDataSet subclass.

Raises

DataSetError – When the function fails to create the data set from its config.

load()

Loads data by delegation to the provided load method.

Return type

Any

Returns

Data returned by the provided load method.

Raises

DataSetError – When underlying load method raises error.

release()

Release any cached data.

Raises

DataSetError – when underlying release method raises error.

Return type

None

save(data)

Saves data by delegation to the provided save method.

Parameters

data (Any) – the value to be saved by provided save method.

Raises

• DataSetError – when underlying save method raises error.

• FileNotFoundError – when save method got file instead of dir, on Windows.

• NotADirectoryError – when save method got file instead of dir, on Unix.

Return type

None