ORACLE COMMAND

Delete: The DELETE command is used to remove rows from a table. A WHERE clause can be used to only remove some rows. If no WHERE condition is specified, all rows will be removed. After performing a DELETE operation you need to COMMIT or ROLLBACK the transaction to make the change permanent or to undo it.

Example- To delete any specific row you would use:

DELETE FROM MyTable WHERE id=5

This would delete the row with the id = 5 If no conditions are matched it would delete all rows

Drop: The DROP command removes a table from the database. All the tables' rows, indexes and privileges will also be removed. No DML triggers will be fired. The operation cannot be rolled back.

Example- DROP TABLE MyTable

This would delete the whole table and its constraints.

ROLLBACK:
To undo the work/changes that are committed or done by COMMIT clause we use the ROLLBACK Command. It is reverse of COMMIT. It rollbacks all the changes of the current transactions. In other words ROLLBACK restore the state of the database to the last commit point.
Syntax
DELETE FROM table_name
ROLLBAC

COMMIT:
Whatever changes we have made/ done in our transaction cannot be fixed until we commit that transaction and this can be possible by using COMMIT statement. In other words it will make our changes permanent that cannot be rolled back.
Syntax

COMMIT;
_____________________________________________________________________________

Alter: Alter is a SQL command that is used to modify, delete or add a column to an existing table in a database. Alter is considered as a DDL statement. Commands that are used to define the structure of a database (database schema) are called DDL statements. Following is the typical syntax of an alter statement that is used to add a column to an existing table.

ALTER TABLE        tableName

ADD                       newColumnName dataTypeOfNewColumn

In here tableName is the name of the existing table that needs to be altered and newColumnName is the name given to the new column that is added to the table. dataTypeOfNewColumn provides the data type of the new column.

Update: Update is a SQL command that is used to update existing records in a database. Update is considered as a DML statement. Commands that are used to manage data without altering the data base schema are called DML statements. Following is the typical syntax of an update statement.

UPDATE                   tableName

SET                          column1Name=value1, column2Name=value2, …

WHERE                    columnXName=someValue

In the above example tableName should be replaced with the name of the table you want to modify the records in. The column1Name, column2Name in the SET clause are the names of the columns in the table in which the values of the record that needs to be modified. value1 and value2 are the new values that should be inserted in the record. WHERE clause specifies the set of records needs to be updated in the table. WEHRE clause could also be omitted from the UPDATE statement. Then all the records in the table would be updated with the values provided in the SET clause.