Hey everyone, welcome back to part nine in topic three of our database class. And in this video, I'm going to show you how you can delete database objects and existing constraints using the SQL drop statement. Oh, that leads us up to where we will begin our new material today. And that is with the drop command. Now in this case, we're reverting back to our DDL part of the broader structured query language. So drop is an element or a statement that belongs to the data definition language. And the purpose of the drop statement is to permanently remove database objects. And as I put here on the slide on the first major bullet point, this is in contrast to removing data. So we're going to drop a table, not only will that delete all of the data in the table, but the structure, the table itself will be removed. So we can do that. Similarly, we can drop like constraints. So if we're, I don't know, establishing a, say, a relationship between tables, and we want to get rid of that relationship, we can use the drop statement. And as it says here, hey, this will permanently remove the object and all of its associated data. So if we're dropping a table, all of the data will be lost forever as will be table itself. And as you can see, the syntax pattern that we use to drop database objects is quite straightforward. We just use the keyword drop in contrast to delete, remember, delete operates on data, but drop operates on database objects, like tables, reviews or relationships or other types of constraints. So delete will remove rows of data from a table, drop can be used to do things like remove the entire table itself. So drop keyword is the first part of our pattern. And then the type of database object we want to drop or get rid of, in this case, a table, and then the name of that object. So very straightforward. Drop table employee means all of the data in the employee table, along with the table itself will be removed from the database. So let's how we use the drop statement. We can also use drop in our in conjunction with the alter statement. So if you remember, a few lessons back, we learned about the alter statement as a way of changing the structure of a database object after it has already been created. So for example, if a table already exists and we wanted to add a new column to the table, we could do that using the alter statement. And the same concept applies here. If the table already exists and we want to remove something about the structure of that table without removing the entire table from the database, then we can use the alter statement in conjunction with drop to accomplish that goal. The example we see here, for example, is removing the foreign key or a foreign key from an employee table. So we assume that the employee table already exists. We assume that it has this constraint, in this case, a foreign key constraint that already exists based on the name we're inferring that it's the foreign key that's connecting this table to the department table. But instead of using the add keyword, we just substitute that with the drop keyword. So if you remember, when we first learned about alter and we were adding things, like adding a new column or adding a constraint like a foreign key, for example, we would use the add keyword here. And everything else is otherwise the same. Right. So all we do is instead of saying add, we say drop and then we specify the whatever it is about that to subject that we would like to drop in this case, a constraint named fk underscore employee department. So that's how we use drop in conjunction with an alter statement. So in this case, we can remove a component of a database object without removing the entire database object. If we want to get rid of a column or in this case, we want to get rid of a foreign key constraint, we can do that.