Insert row into a table using Python

This notebook will show you how to insert rows into table. Remember that when row is inserted and you want to remove it, you need to do it manually.

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Documentation

All required packages are automatically imported by MLJAR Studio for you so you don't have to worry about them.

# import packages
import psycopg
import os
from dotenv import load_dotenv
from psycopg import sql

Make sure you opened a connection in your notebook. To learn how to do it, check out open and test database connection example notebook.

# load credentials from .env file:
load_dotenv(override=True)

# get the credentials
def create_new_connection():
    try:
        conn = psycopg.connect(
            dbname=os.getenv("POSTGRES_DB_NAME"),
            user=os.getenv("POSTGRES_USERNAME"),
            password=os.getenv("POSTGRES_PASSWORD"),
            host=os.getenv("POSTGRES_HOST"),
            port=os.getenv("POSTGRES_PORT"),
        )
        return conn
    # check for errors
    except psycopg.Error as e:
        raise psycopg.Error(f"""
Error occurred while establishing connection: 
    {e}

Maybe you provided wrong credentials, use define new connection recipe to edit them.
Other option is that database server is down or you dont have the right acces to this database.
            """)

# open new connection:
conn = create_new_connection()

We will perform the update in table test. Lets list all columns of that table using show all columns recipe

# if connection was used and closed it is reopen here
if conn.closed:
    conn = create_new_connection()

# run query
with conn:
    with conn.cursor() as cur:

        # query db
        try:
            cur.execute("""
                    SELECT attname AS col, atttypid::regtype AS datatype
                    FROM pg_attribute
                    WHERE attrelid = %s::regclass 
                    AND attnum > 0
                    AND NOT attisdropped
                    ORDER BY attnum;""", 
                    ("test",))
        # check for errors
        except psycopg.ProgrammingError as e:
            raise psycopg.ProgrammingError(f"""
Problem running query:
    {e}

Did you spell everything correctly?
You can use show tables and columns recipes.
            """)

        # print the results
        print("Columns of test:")
        for column in cur.fetchall():
            print(f"{column}")

Our insert will be into num and data columns, we can omit id column because it's auto generated. If you omint columns that are not auto generated a null value will get inserted. Lets check show result option to display new rows.

# if connection was used and closed it is reopen here
if conn.closed:
    conn = create_new_connection()

# run query
with conn:
    with conn.cursor() as cur:

        # insert into db
        try:
            cur.execute(
                sql.SQL(
                    "INSERT INTO {table} ({columns}) VALUES (%s, %s) RETURNING *"
                ).format(
                    table=sql.Identifier("test"),
                    columns=sql.SQL(",").join(
                        [sql.Identifier(column) for column in ["num","data"]]
                    ),
                ),
                ("2121","very interesting piece of text",),
            )
        # check for errors
        except psycopg.ProgrammingError as e:
            raise psycopg.ProgrammingError(f"""
Problem running query:
    {e}

Are you sure every name is spelled correctly?
You can use show all tables or columns to check db contents.
            """)

        # print the results
        while True:
            for row in cur.fetchall():
                print(row)
            if not cur.nextset():
                break

To see our changes in context we'll run select query. Lear how to use it here.

# if connection was used and closed it is reopen here
if conn.closed:
    conn = create_new_connection()

# run query
with conn:
    with conn.cursor() as cur:

        # query db
        try:
            cur.execute(
                sql.SQL("SELECT {columns} FROM {table}").format(
                    columns=sql.SQL("*"),
                    table=sql.Identifier("test"),
                )
            )
        # check for errors
        except psycopg.ProgrammingError as e:
            raise psycopg.ProgrammingError(f"""
Problem running query:
    {e}

Did you spell everything correctly?
You can use show tables and columns recipes.
            """)

        # print the results
        for row in cur.fetchall():
            print(f"{row}")

Conclusions

With this new learned knowledge you can insert into columns as much as you would ever like!

Recipes used in the postgresql-python-insert-query.ipynb

All code recipes used in this notebook are listed below. You can click them to check their documentation.

Packages used in the postgresql-python-insert-query.ipynb

List of packages that need to be installed in your Python environment to run this notebook. Please note that MLJAR Studio automatically installs and imports required modules for you.

psycopg>=3.2.1

python-dotenv>=1.0.1

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