How to clear table data in oracle

Oracle method to clear table data: 1. Use the TRUNCATE TABLE statement to delete all rows in the table, but retain the table structure, indexes, constraints, etc.; 2. Use the DELETE statement to delete the table rows, and you can select rows to be deleted based on conditions; 3. Use the DROP TABLE statement to delete the entire table, including table structure, indexes, constraints, etc.

To clear the data in the Oracle table, you can use the following methods:

1. Use the TRUNCATE TABLE statement: The TRUNCATE TABLE statement is used to delete All rows in the table, but retaining the table structure, indexes, constraints, etc. It is faster than the DELETE statement because it does not record the operation of each row, but directly releases the table space. The syntax for using the TRUNCATE TABLE statement is as follows:

TRUNCATE TABLE table_name;

Among them, table_name is the name of the table to clear the data.

For example, to clear the table data named "employees", you can execute the following statement:

TRUNCATE TABLE employees;

Note: The TRUNCATE TABLE statement will immediately delete all data in the table and cannot be undone. Therefore, please make sure you have backed up important data before executing this statement.

2. Use the DELETE statement: The DELETE statement is used to delete rows in the table, and the rows to be deleted can be selected based on conditions. If you do not specify a condition, all rows in the table will be deleted. The syntax for using the DELETE statement is as follows:

  DELETE FROM table_name [WHERE condition];

Among them, table_name is the name of the table to clear the data, and condition is the condition to be met (optional).

For example, to clear all data in the table named "employees", you can execute the following statement:

DELETE FROM employees;

If you only want to delete rows that meet a certain condition, you can use the DELETE statement Add WHERE clause. For example, to delete all employee records with the department "IT", you can execute the following statement:

DELETE FROM employees WHERE department = 'IT';

Note: The DELETE statement will delete the data in the table row by row and record the operation of each row, so the execution speed slower. If you just want to clear all the data in the table, it is recommended to use the TRUNCATE TABLE statement.

3. Use the DROP TABLE statement: The DROP TABLE statement is used to delete the entire table, including table structure, indexes, constraints, etc. After executing this statement, the table no longer exists. The syntax for using the DROP TABLE statement is as follows:

DROP TABLE table_name;

Among them, table_name is the name of the table to be deleted.

For example, to clear the data in the table named "employees" and delete the table, you can execute the following statement:

DROP TABLE employees;

Note: The DROP TABLE statement will delete the entire table immediately and cannot Undo. Therefore, before executing this statement, make sure you have backed up important data and make sure you really want to delete the entire table.

Summary

You can use the TRUNCATE TABLE statement or DELETE statement to clear the data in the Oracle table. If you just want to clear the data and retain the table structure, it is recommended to use the TRUNCATE TABLE statement; if you need to selectively delete data based on conditions, or if you want to delete the entire table, you can use the DELETE statement or DROP TABLE statement. No matter which method is used, you should back up your data before executing it and operate with caution.

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