SQL DROP / DELETE
The DROP command is used to remove an object/table
from the database and database also by “DROP DATABASE” command. If you
want to drop a table using “DROP TABLE” command, all the rows in the
table are deleted and the table structure is removed from the database. Once a
table is dropped we cannot get it back table and its records, so be careful
while using DROP command because “DROP” Command removed the records of
the table with deleting the structure of table also. When a table is dropped
all the references to the table will not be valid.
Syntax:
DROP TABLE tableName;
Following is the example DROP CUSTOMERS table permanently from the database,
Once CUSTOMERS table deleted from database, It can’t be recovered.
SQL > DROP TABLE CUSTOMERS;
Query Ok – Table Dropped
SQL
DELETE
The
SQL DELETE Query is used to delete the existing records from a table.
You
can use WHERE clause with DELETE query to delete selected rows, otherwise all
the records would be deleted.
Syntax:
DELETE
FROM table_name
WHERE
[condition];
You
can combine N number of conditions using AND or OR operators.
Example:
Consider
the CUSTOMERS table having the following records:
+----+-------------+------+-----------------+---------------+
|
ID | NAME | AGE
| ADDRESS | SALARY |
+----+-------------+------+-----------------+---------------+
|
1 | Ramesh | 32
| Ahmedabad | 2000.00 |
|
2 | Khilan | 25
| Delhi |
1500.00 |
|
3 | kaushik | 23
| Kota |
2000.00 |
|
4 | Chaitali | 25
| Mumbai | 6500.00 |
|
5 | Hardik | 27
| Bhopal | 8500.00 |
|
6 | Komal | 22
| MP |
4500.00 |
|
7 | Muffy | 24
| Indore |
10000.00 |
+----+-------------+------+-----------------+---------------+
Following is an
example, which
would DELETE a customer, whose ID is 6:
SQL>
DELETE FROM CUSTOMERS
WHERE
ID = 6;
Now,
CUSTOMERS table would have the following records:
Consider
the CUSTOMERS table having the following records:
+----+-------------+------+-----------------+---------------+
|
ID | NAME | AGE
| ADDRESS | SALARY |
+----+-------------+------+-----------------+---------------+
|
1 | Ramesh | 32
| Ahmedabad | 2000.00 |
|
2 | Khilan | 25
| Delhi |
1500.00 |
|
3 | kaushik | 23
| Kota |
2000.00 |
|
4 | Chaitali | 25
| Mumbai | 6500.00 |
|
5 | Hardik | 27
| Bhopal | 8500.00 |
|
7 | Muffy | 24
| Indore |
10000.00 |
+----+-------------+------+-----------------+---------------+
If you
want to DELETE all the records from CUSTOMERS table, you do not need to use
WHERE clause and DELETE query would be as follows:
SQL>
DELETE FROM CUSTOMERS;
Now, CUSTOMERS
table would not have any record.
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