oracle changes data

Oracle Change Data

Oracle database is the most commonly used enterprise-level database in the world. Due to its advantages in reliability, performance and other aspects, it is widely used in enterprise-level applications. Changing data is a common need when working with Oracle databases. This article will introduce methods and considerations for changing data in Oracle database.

1. How to change data

1. Use the UPDATE command

The UPDATE command is the most commonly used command to change data in the Oracle database. Use the UPDATE command to modify the data in the table. The syntax is as follows:

UPDATE table name SET column name 1=value 1, column name 2=value 2,... WHERE condition;

where, table The name is the name of the table to be modified, the column name is the name of the column to be modified, the value is the new value to which the column is to be modified, and the WHERE clause is used to specify the conditions for the data to be modified. For example, the following SQL statement increases the salary of all people with the last name "Zhang" in the table by 10%:

UPDATE employees SET salary = salary * 1.1 WHERE last_name = 'Zhang';

2. Use the MERGE command

The MERGE command can merge data from one table into another table. If there is a conflict between the data to be inserted and the data in the target table, you can update the target table. The data. The syntax is as follows:

MERGE INTO target table USING table to be merged ON condition WHEN MATCHED THEN UPDATE SET target table column = table column to be merged WHEN NOT MATCHED THEN INSERT (column name 1, column name 2, ...) VALUES (value 1, value 2, ...);

where the target table is the name of the table to be merged, the table to be merged is the name of the table to be merged, and the condition is used to specify the table to be merged Which rows in the target table should the data in be inserted into, and the SET clause is used to specify which column values ​​in the target table should be updated. For example, the following SQL statement merges data from the employees table into the employee list:

MERGE INTO employees_list USING employees ON employees_list.employee_id = employees.employee_id WHEN MATCHED THEN UPDATE SET employees_list.salary = employees.salary WHEN NOT MATCHED THEN INSERT (employee_id, last_name, salary) VALUES (employees.employee_id, employees.last_name, employees.salary);

3. Use INSERT INTO SELECT command

INSERT INTO The SELECT command can insert data from one table into another table. The syntax is as follows:

INSERT INTO table name (column name 1, column name 2, ...) SELECT column name 1, column name 2 , ... FROM original table WHERE condition;

where the table name is the name of the table into which data is to be inserted, the column name is the name of the column into which data is to be inserted, and the original table is the original table into which data is to be inserted. Name, condition used to specify which rows to select from the original table. For example, the following SQL statement inserts all employees with a salary greater than 5000 in the employees table into the employees list:

INSERT INTO employees_list(employee_id, last_name, salary) SELECT employee_id, last_name, salary FROM employees WHERE salary > 5000;

2. Precautions for changing data

1. Using transactions

Data changes may affect the integrity and consistency of the database. Therefore, when changing data, transactions should be used to ensure the correctness and consistency of the data. If changes fail, the transaction should be rolled back, undoing the changes. The following is an example of using transactions in PL/SQL:

DECLARE BEGIN --Open the transaction SAVEPOINT start_tran; --Perform the operation of changing data UPDATE employees SET salary = salary * 1.1 WHERE last_name = 'Zhang'; - -Commit transaction COMMIT; EXCEPTION --If an error occurs, roll back the transaction ROLLBACK TO SAVEPOINT start_tran; END;

2. Use DELETE command carefully

DELETE command is used to delete data in the table, but if you use the DELETE command accidentally, you may delete data that should not be deleted. Be careful when using the DELETE command and back up your data in advance just in case.

3. Use the correct data type

When changing data, you should use the correct data type to ensure the integrity and correctness of the data. If you use the wrong data type, it may cause problems such as overflow or truncation of data. For example, if you change a column that contains characters to a column that contains numeric values, an error may occur.

4. Confirm changes

Before changing data, you should confirm which data you want to change and make sure these changes are correct. If you change the wrong data, it can have serious consequences.

Conclusion

When using Oracle database, changing data is a common need. This article describes methods and considerations for changing data in an Oracle database. By using these statements and techniques correctly, you can better manage and maintain your Oracle database and ensure data integrity and correctness.

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