MongoDB Database Basics (Day 3)

The “switched to db Demo2” message shows that we have been switched to the Demo2 database.

show dbs

This command is used to show the database name.

Syntax: show dbs

Example



In the preceding example, we run the “show dbs” command and retrieve all the database names that exist. Now we see another example.

First of all, create a new database <Demo_Test> as in the following:



Now we are executing the “show dbs” command and the output will be as in the following:



We can see that the Demo_Test database is not present in the preceding list. Now the question is, why is our database not visible? The reason is that we created an empty database. So the size of the database is zero.

Now we create a collection in the Demo_Test database and then again execute the “show dbs” command.



Now we can see that the Demo_Test database is present in the preceding list.

Note: We can see that the size of our database is 0.078 GB. This is the minimum (default) size of any database. the size of the database will increase when the size of the existing data exceeds 0.078 GB.



Db Command

The db command shows the current selected database name.

Syntax: db

Let's see an example.



If a database is not selected, then the “db” command will show the “test” database name. test is the system database.



dropDatabase Command

The dropDatabase() command deletes the selected database. First, select a database and then use the dropDatabase() command.

Syntax: db.dropDatabase()

Example

First, we check the list of available databases using the command show dbs.



If we want to delete the Demo_Test database, then first select the Demo_Test database and then run the dropDatabase() command.



Now check the database list again.



We can see that the Demo_Test database does not exist in the preceding list. In other words, this database has been deleted.

Note:

Next article >> MongoDB Collection (Day 4)