Pandas merge() and read_sql() — joining DataFrames.

I have written several articles recently, about pandas and PostgreSQL database interaction — specifically in loading CSV data. In this post, I’ll cover what I have recently learned using pandas merge() and read_sql_query(), retrieving query results using ‘s and similar queries.

Photo by pine watt on Unsplash

OS, Database, and software used:

• Xubuntu Linux 18.04.2 LTS (Bionic Beaver)
• PostgreSQL 11.4
• Python 3.7.4
• pandas-0.25.0

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Feel free to visit these similar posts about pandas and SQL…

• Pandas to SQL — importing CSV data files into PostgreSQL
• Basic CSV file import and exploration with Pandas — first steps.
• Pandas concat() then to_sql() — CSV upload to PostgreSQL

For starters, I import pandas, SQLAlchemy, and create a connection to the PostgreSQL database:

>>> import pandas as pd
>>> import sqlalchemy
>>> from sqlalchemy import create_engine
>>>…