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‎README.md‎

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# Connect PostgreSQL database with Python
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In this section, I'll explain how to connect your PostgreSQL database to Python and query it.
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## Install "Psycopg2"
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To access the PostgreSQL database, Python needs a PostgreSQL driver. You must first install the `Psycopg2` package on your computer.
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```bash
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python -m pip install psycopg2
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python -m pip install psycopg2
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```
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## Import Psycopg2"
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To access the PostgreSQL database, import `psycopg2` library into your Python code.
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```python
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import psycopg2
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import psycopg2
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```
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## Creating a Database:
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For the purpose of example, we will need a sample database. To do so, follow the below steps:
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- First, open a PostgreSQL client tool like `pgadmin4` or `psql`.
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- Second login to the database using your credentials.
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- Finally, run the following command to create a database (for example, `company`).
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```sql
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CREATE DATABASE company;
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CREATE DATABASE company;
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```
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## Create Connection:
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To connect to the above created database (i.e., `company`), we use the `connect()` function.
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So, establish a connection to the database. Use your PostgreSQL database's username and password in the Python code.
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```python
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mydb = psycopg2.connect(
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host="localhost",
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user="yourUsername",
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password="yourPassword",
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database="company"
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)
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mydb = psycopg2.connect(
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host="localhost",
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user="yourUsername",
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password="yourPassword",
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database="company"
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)
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```
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## Make Cursor:
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You must create or include a `cursor()` in your Python code in order to run SQL queries.
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```python
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mycursor = mydb.cursor()
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mycursor = mydb.cursor()
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```
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Now you can use SQL commands to query the database.
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## Commit Changes:
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You also have to include the commit function and set automatic commit to be `true`.
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```python
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mydb.set_session(autocommit=True)
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mydb.set_session(autocommit=True)
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```
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So that each action is committed or saved without having to call `mydb.commit()` after each command.
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## Query the Database:
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Now create a table in the database using the cursor we created.
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```python
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mycursor.execute('''CREATE TABLE employee(
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EmployeeID int,
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Name varchar(255),
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Email varchar(255));
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''')
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mycursor.execute('''CREATE TABLE employee(
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EmployeeID int,
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Name varchar(255),
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Email varchar(255));
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''')
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```
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## Insert Data Into Table:
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Now we are inserting the values into the database.
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```python
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mycursor.execute('''
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INSERT INTO employee (EmployeeID, Name, Email)
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VALUES (101, 'Mark', 'mark@company.com'),
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(102, 'Robert', 'robert@company.com'),
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(103, 'Spencer', 'spencer@company.com');
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''')
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mycursor.execute('''
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INSERT INTO employee (EmployeeID, Name, Email)
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VALUES (101, 'Mark', 'mark@company.com'),
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(102, 'Robert', 'robert@company.com'),
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(103, 'Spencer', 'spencer@company.com');
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''')
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```
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## Retrive the Data:
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Now let’s query the database.
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```python
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mycursor.execute("SELECT * FROM employee")
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mycursor.execute("SELECT * FROM employee")
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```
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It’s important to note that after the query executes, you still need to use one of the `psycopg2` functions to retrieve data rows.
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- fetchone()
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- fetchall()
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- fetchmany()
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For example,
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```python
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print(mycursor.fetchone())
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print(mycursor.fetchone())
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```
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| EmployeeID | Name | Email |
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| :--------- | :------- | :---------------- |
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| 101 | Mark | mark@company.com |
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The most basic way to fetch data from your database is to use the `fetchone()` function. This function will return exactly one row (the first row) after executing the SQL query.
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| EmployeeID | Name | Email |
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| :--------- | :--- | :--------------- |
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| 101 | Mark | mark@company.com |
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The most basic way to fetch data from your database is to use the `fetchone()` function. This function will return exactly one row (the first row) after executing the SQL query.
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```python
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print(mycursor.fetchall())
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print(mycursor.fetchall())
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```
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| EmployeeID | Name | Email |
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| :--------- | :------- | :---------------- |
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| 101 | Mark | mark@company.com |
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| 102 | Robert | robert@company.com |
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| 103 | Spencer | spencer@company.com |
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| EmployeeID | Name | Email |
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| :--------- | :------ | :------------------ |
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| 101 | Mark | mark@company.com |
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| 102 | Robert | robert@company.com |
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| 103 | Spencer | spencer@company.com |
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If you need more than one row from your database, you can use `fetchall()`, which works the same as `fetchone()` except that it returns all the rows.
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```python
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print(mycursor.fetchmany(2))
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print(mycursor.fetchmany(2))
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```
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| EmployeeID | Name | Email |
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| :--------- | :------- | :---------------- |
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| 101 | Mark | mark@company.com |
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| 102 | Robert | robert@company.com |
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| EmployeeID | Name | Email |
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| :--------- | :----- | :----------------- |
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| 101 | Mark | mark@company.com |
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| 102 | Robert | robert@company.com |
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With `fetchmany()`, you have another option to retrieve multiple records from the database and have more control over the exact number of rows retrieved.
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You can use any of them depending on your needs.
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You can use any of them depending on your needs.
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## Close the Connection:
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In the end, you must close the cursor and the connection.
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```python
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mycursor.close()
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mydb.close()
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mycursor.close()
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mydb.close()
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```
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You can also get code snippet from [here](https://github.com/kishlayjeet/Connect-PostgreSQL-database-to-Python/blob/d7c5cae0a809ec0714cf193c5db6a77f30e70502/code-snippet.py).
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## Authors
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I am [Kishlay](https://www.github.com/kishlayjeet), and I have written this tutorial, but other people have also helped me with it.
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If you have any trouble with this tutorial, please tell me about it, and I will make it better.
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If you like this tutorial and this helped you out, then please give it a star.
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## Feedback
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If you have any feedback, please reach out to me at contact.kishlayjeet@gmail.com
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If you have any feedback, please reach out to me at contact.kishlayjeet@gmail.com

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