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Basic concept of database management system (a concept of a DBMS learner)

Basic concept of database management system

                                                        a concept of a DBMS learner

In past two post we learn:

1. how to show a database
2. how to create a database
3. how to show a table
4. how to create a table
5. how to insert data into table &
6. how to see the data existing in a table
7. How to update data in atable

      Click here to see video more like this

                 Today we learn how to delete data from a table.

      The DELETE statement is used to delete rows in a table. It's very simple. To delete any data in a  table of a DBMS we follow the given syntax:

                    DELETE FROM table_name 

                    WHERE some_column=some_value;

The WHERE clause specifies which record or records that should be deleted. If you omit the WHERE clause, all records will be deleted!

To delete all data from a table we use following syntax:

                   DELETE FROM table_name;

                                       or

                   DELETE * FROM table_name;

Lets consider some example to get the concept clear. There  are  three data in the table "table_name" given below in a picture:

We can insert data in a table. Today we learn how to delete data from a table. Before delete we want to insert some data to cheek that we can insert & after inserting we again delete those data. Let insert two more row in the table "Table_name".

We know what to do to insert data in a table. It's look like below:

Insert into table_name values (4,'fata','fata@mail.com');

insert into table_name values (5,'sata','sata@mail.com');

Data is inserted & we get like following picture:

Wow! we can insert data into table & we must be able to delete data after  a few moment. I don't want to spent anymore time. Lets start .....

Firstly we want to delete specific row/ rows from table. For this reason we have to follow the following rules:

                                          DELETE FROM table_name 

                                          WHERE some_column=some_value;

One example can make the concept clear.If we want to delete id no 5 with its all records then we have to write:

                                         delete from table_name where id='5';

If it shows a massage containing "Query Ok, 1 row affected (0.01 sec)" like following picture then we almost done mean we successfully delete that data.

Now write the command to show data from a table that means   select *from table_name;  & get the following picture:

Notice that the id no 5 & its all record is deleted. It clarify from the following picture:

Now again write   delete from table_name where name='fata'; then it will delete the entire raw of id 4. And we get like following picture:

Here where clause mention data linking mean which data will be delete.

Now we learn delete entire data of a table. To do so we have to write:

                                                     delete  from table_name;

                                                                  or

                                                    delete * from table_name;

Write any one of two command to delete entire data from the table.

The above picture show that "Query Ok, 3 rows affected (0.01 sec) mean it delete three row of the table. 

When we write select *from table_name; then it tells us Empty set (0.0 sec) mean all data deleted

Is it so tough? Obviously not. So keep trying.

Note: any correction or suggestion warmly received.