It's time to get back to writing queries and consider two more statements.

You already know how to clear a table, add a column, insert data, etc. But for proper interaction with the database, we need to understand how to update and delete individual rows.

For this, there are two statements and types of queries: the UPDATE and the DELETE queries.

UPDATE

UPDATE: Used to modify existing data in a table. With such a query, we can change data in a table without affecting other rows. Let's look at an example with the medications table, which looks like this:

Let's imagine we need to update the price for a specific type of medication. For example, currently, there's a 50% discount on ibuprofen, and we need to change the price for this product.

Our update query will look like this:

Here, we updated the medications table so that the price for the product with id 2 (ibuprofen) will be set to 4. After that, we selected all the columns from the table to ensure the price column was successfully updated. You can substitute any value and see how the update operation works in SQL.

In summary, the general syntax looks like this:

DELETE

The operation of the DELETE statement is almost identical in principle. However, here we do not use the keyword SET because we are not changing anything; we are simply deleting rows.

The syntax for deletion will look like this:

But I'll remind you that deleting rows should be done with caution, as you won't be able to simply recover them.

Note

If you don't include a WHERE condition, the data will be updated or deleted for all rows.

Let's move on to the practice!