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1. Python create sqlite database update#
2. Python create sqlite database code#
3. Python create sqlite database series#

In order to delete a record, we must call the DELETE statement with the id of the object we want to remove.For the same schema, we will be writing related SQL Query next and these queries will be saved in book_schema.sql:

Python create sqlite database update#

Query = " UPDATE products SET quantity = (quantity + ?) WHERE id = ? "Įxecute( conn, query, (quantity, productId)) def updateProductQuantity(conn, productId, quantity): We will need to update the product's stock, so we will need a positive or negative quantity to add or subtract from the current stock. Think of the DataFrame as a table, a pretty formatted one. The read_sql_query function returns a DataFrame corresponding to the result set of the query string. Pd is the alias for pandas, a library that really helps when it comes to showing and manipulating data, we need to import it at the top of our python program like this import pandas as pd.

Query = "SELECT * FROM products " print (pd.read_sql_query(query, conn)) To read every record that is stored in a table, we will use the SQL Select statement def selectAllProducts( conn): To insert a product you can follow along with that pattern. See how tiny the function is? That's because we wrote execute and create_connection before. The supplier argument should be a list with the value (name, address). Query = " INSERT INTO SUPPLIERS ( name, address) VALUES (?,?) " So now to insert a supplier we will make a function like this def insertSupplier(conn, supplier): Without this function we will be repeating the conn.execute and mit every time we need to execute a query.

Python create sqlite database code#

Now, what is that execute function at the end? We need to code that. That foreign key considers this part of the problem: "Every product they have is only bought from one supplier". The "IF NOT EXISTS" will allow us to create them only if they already don't exist. Query = """CREATE TABLE IF NOT EXISTS products (įOREIGN KEY(supplier_id) REFERENCES suppliers(id) Query = """CREATE TABLE IF NOT EXISTS suppliers ( We may need to create our tables, that would be handled by the functions createProducts and createSuppliers def createSuppliers( conn): # We perform operations to the database inside the with statement # It is a much readable way, and we can omit to close the connection # with can handle it Creating our tables Now we can in the main program, call it like this def main():ĭBFILE = "db.sqlite3" # You can choose any name you want We can do it directly, but we are going to get the connection from the main program calling the function create_connection that will receive db (the file path of the database) and return the connection def create_connection( db): We need to start a connection with the SQLite database, which is nothing more than a file. Of course, it could be less, for the sake of the tutorial I wanted to portrait all the basic CRUD operations (Create/Read/Update/Delete) The Code Setting up database We are going to allow the user the perform eight operations We can make a diagram of our database and it will look like this Our database diagram and the relation between tables

Python create sqlite database series#

If you also never coded a line a Python, the series in Layla's blog that starts with Python basics it's going to help you out. To perform actions over that set of data, we are going to use python.Īre you absolutely new to the SQL world? You can start reading "Essential SQL for beginners" by Shreyas Kulkarni. We are going to use SQLite, a popular relational database management system that does not require a lot of configuration to start using, it is rather embedded into the final program. This version uses no classes, so, if you are new to this, you can follow along with no problems. It's a simplified version of a real problem I solved a few months ago. I believe that real knowledge strikes in when you apply a concept to a real situation.

I'm a person who is not a big fan of the "foo, bar, baz" examples.