Deleting Data
**Deleting data from a SQL database means removing existing records from a table. **Think of it like erasing a row from a spreadsheet.
You might want to delete data from a database for a variety of reasons. For example, if a customer closes their account, you might want to remove their record from your customers table. If a product is no longer sold, you might want to delete its record from your products table.
Be careful!
It's important to note that deleting records is a significant action. Once a record is deleted, it's gone. Many databases don't have an 'undo' option for a delete operation, so you have to be sure you want to remove a record before doing so.
Using the DELETE Keyword
To delete data, you use the DELETE command in SQL. Usually, this command is combined with a WHERE clause to specify which record or records should be deleted.
For instance, if you wanted to delete a customer named 'Smith' from your customers table, you would use a command like this:
DELETE FROM customers
WHERE customer_name = 'Smith';This command tells the database to find the customers table, find the record where the customer_name is 'Smith', and delete that record.
Always Add a WHERE Clause
Just like with the UPDATE command, you need to be careful with your WHERE clause when using the DELETE command. If your WHERE condition is not specific enough, you could end up deleting more records than you intend. Without a WHERE clause at all, the DELETE command would delete all records in the table!
Key Takeaways
- Deleting data in SQL refers to removing existing records from a table.
- The
DELETEstatement is used to remove records from a table in SQL. - Deleting is a significant action because once a record is deleted, it's permanently gone from the table.