Alternative to_sql() *method* for mssql+pyodbc

mssql_insert_json.py

# Alternative to_sql() *method* for mssql+pyodbc or mssql+pymssql
#
# adapted from https://pandas.pydata.org/docs/user_guide/io.html#io-sql-method
#
# version 1.6 - 2024-03-28
from datetime import date
import json

import pandas as pd
import sqlalchemy as sa


def mssql_insert_json(table, conn, keys, data_iter):
    """
    Execute SQL statement inserting data via OPENJSON

    Parameters
    ----------
    table : pandas.io.sql.SQLTable
    conn : sqlalchemy.engine.Engine or sqlalchemy.engine.Connection
    keys : list of str
        Column names
    data_iter : Iterable that iterates the values to be inserted
    """
    # build dict of {"column_name": "column_type"}
    col_dict = {
        str(col.name): "nvarchar(max)"
        if str(col.type) in ["TEXT", "NTEXT"]
        else "bit"
        if str(col.type) == "BOOLEAN"
        else "datetime2"
        if str(col.type) == "DATETIME"
        else str(col.type)
        for col in table.table.columns
    }
    columns = ", ".join([f"[{k}]" for k in keys])
    if table.schema:
        table_name = f"[{table.schema}].[{table.name}]"
    else:
        table_name = f"[{table.name}]"

    json_data = [dict(zip(keys, row)) for row in data_iter]

    with_clause = ",\n".join(
        [
            f"[{col_name}] {col_type} '$.\"{col_name}\"'"
            for col_name, col_type in col_dict.items()
        ]
    )
    placeholder = "?" if conn.dialect.paramstyle == "qmark" else "%s"
    sql = f"""\
    INSERT INTO {table_name} ({columns})
    SELECT {columns}
    FROM OPENJSON({placeholder})
    WITH
    (
    {with_clause}
    );
    """

    conn.exec_driver_sql(sql, (json.dumps(json_data, default=str),))


if __name__ == "__main__":
    # =============
    # USAGE EXAMPLE
    # =============

    # note: fast_executemany=True is not required
    engine = sa.create_engine("mssql+pyodbc://scott:tiger^5HHH@mssql_199")

    df = pd.DataFrame(
        [(1, "Cheers!", date(2001, 1, 1)), (2, "ΟΠΑ!", date(2002, 2, 2))],
        columns=["id", "my text", "date added"],
    )

    df.to_sql(
        "##tmp",
        engine,
        index=False,
        if_exists="append",
        dtype={"my text": sa.types.UnicodeText},
        method=mssql_insert_json,
    )

    # check result
    with engine.begin() as connection:
        print(connection.exec_driver_sql("SELECT * FROM ##tmp").all())
        # [(1, 'Cheers!', datetime.date(2001, 1, 1)), (2, 'ΟΠΑ!', datetime.date(2002, 2, 2))]

"""The INSERT statement generated for this example is:

INSERT INTO [##tmp] ([id], [my text], [date added])
SELECT [id], [my text], [date added]
FROM OPENJSON(?)
WITH
(
[id] BIGINT '$."id"',
[my text] nvarchar(max) '$."my text"',
[date added] DATE '$."date added"'
);

"""