To delete records in Oracle, you can use the DELETE statement. The basic syntax for deleting records is as follows:
DELETE FROM table_name WHERE condition;
Here, "table_name" refers to the name of the table from which you want to delete records. The "WHERE" clause is used to specify the condition that must be met for a record to be deleted. If you omit the WHERE clause, all records from the table will be deleted.
For example, if you have a table named "employees" and you want to delete the records where the employee_id is 123, you can use the following command:
DELETE FROM employees WHERE employee_id = 123;
This statement will delete all records from the "employees" table where the employee_id is 123.
It's important to note that when you delete records from a table, the data is permanently removed from the database. Therefore, exercise caution and ensure that you have appropriate backups or confirmation before proceeding with a delete operation.
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How to delete records and rollback changes in Oracle?
To delete records and rollback changes in Oracle, you can use the DELETE statement and the ROLLBACK command. Here's how you can do it:
- Connect to Oracle database using SQL*Plus or any other Oracle client tool.
- Start a new transaction by issuing the BEGIN TRANSACTION command or set the autocommit mode to off if you want to manually control the transaction.
- Write a DELETE statement to remove the desired records from the table. For example, to delete all records from a table named "employees" where the salary is less than 50000, you can use the following statement:
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DELETE FROM employees WHERE salary < 50000;
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- Execute the DELETE statement by running the command in your Oracle client.
- If you want to verify that the deletion has been successful, you can run a SELECT statement before issuing the ROLLBACK command. For example:
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SELECT * FROM employees;
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- If you are satisfied with the deletion and want to make it permanent, you can issue the COMMIT command to save the changes to the database. For example:
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COMMIT;
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- However, if you want to rollback the changes and restore the deleted records, you can issue the ROLLBACK command. For example:
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ROLLBACK;
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- After executing the ROLLBACK command, the deleted records will be restored, and the database will be in the state before the transaction started.
Remember to be cautious while using the DELETE statement and to verify the conditions and records you are deleting before committing changes or issuing the ROLLBACK command, as it cannot be undone once committed.
How to delete records from a specific table in Oracle?
To delete records from a specific table in Oracle, you can use the DELETE statement.
The basic syntax of the DELETE statement is:
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DELETE FROM table_name WHERE condition;
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- table_name is the name of the table from where you want to delete records.
- condition is an optional parameter that specifies the condition that must be met for a record to be deleted. If you omit the condition, all records from the table will be deleted.
Here's an example of how to delete records from a table called "employees" where the employee ID is 100:
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DELETE FROM employees WHERE employee_id = 100;
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If you want to delete all records from the table, simply omit the WHERE clause:
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DELETE FROM employees;
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Note: Exercise caution while performing deletion operations as it permanently removes the records from the table. It is recommended to take a backup of the table before deleting records.
How to delete records from a partitioned table in Oracle?
To delete records from a partitioned table in Oracle, you can use the DELETE statement with the PARTITION clause. Here is an example:
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DELETE FROM table_name PARTITION (partition_name) WHERE condition; |
Replace table_name with the name of your partitioned table, partition_name with the name of the specific partition you want to delete records from, and condition with the criteria for selecting the records to delete.
Alternatively, you can also use the ALTER TABLE statement to truncate a specific partition, effectively deleting all records within it:
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ALTER TABLE table_name TRUNCATE PARTITION partition_name;
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Again, replace table_name with the name of your partitioned table and partition_name with the name of the specific partition you want to truncate/delete records from.
Note that deleting records from a partitioned table requires appropriate privileges, and it's important to be careful when performing such operations as they can potentially affect a large amount of data.
