Let's see an example of the EMPLOYEE table:
In the above table, "EMPLOYEE" is the table name, "EMP_ID", "EMP_NAME", "CITY", "PHONE_NO" are the column names. The combination of data of multiple columns forms a row, e.g., 1, "Kristen", "Washington" and 7289201223 are the data of one row.
Operation on Table
SQL Create Table
SQL create table is used to create a table in the database. To define the table, you should define the name of the table and also define its columns and column's data type.
If you create the table successfully, you can verify the table by looking at the message by the SQL server. Else you can use DESC command as follows:
SQL> DESC EMPLOYEE;
Now you have an EMPLOYEE table in the database, and you can use the stored information related to the employees.
A SQL drop table is used to delete a table definition and all the data from a table. When this command is executed, all the information available in the table is lost forever, so you have to very careful while using this command.
Firstly, you need to verify the EMPLOYEE table using the following command:
This table shows that EMPLOYEE table is available in the database, so we can drop it as follows:
Now, we can check whether the table exists or not using the following command:
As this shows that the table is dropped, so it doesn't display it.
SQL DELETE table
In SQL, DELETE statement is used to delete rows from a table. We can use WHERE condition to delete a specific row from a table. If you want to delete all the records from the table, then you don't need to use the WHERE clause.
Suppose, the EMPLOYEE table having the following records:
The following query will DELETE an employee whose ID is 2.
Now, the EMPLOYEE table would have the following records.
If you don't specify the WHERE condition, it will remove all the rows from the table.
Now, the EMPLOYEE table would not have any records.