oracle modify table data

Oracle is a widely used relational database management system that is widely used in enterprise-level data management. In the process of using Oracle database, modifying table data is one of the most basic operations. However, this operation is also prone to problems, so you must be cautious before making modifications.

The following introduces some common methods and techniques on how to modify table data in Oracle.

1. Use the UPDATE statement to modify data

The most common way to modify table data is to use the UPDATE statement. The UPDATE statement is used to update data in the table. Normally, the following conditions need to be met for data modification:

1) Determine the rows to be modified

2) Determine the columns to be modified

3) Determine the columns to be modified Value

For example, if you want to change the addresses of all customers in the customer table to "Haidian District, Beijing", you can use the following statement:

UPDATE customer SET address = '北京市海淀区';

If you only need to modify a specific customer The address can be specified with the WHERE clause:

UPDATE customer SET address = '北京市海淀区' WHERE customer_id = 1;

2. Use the MERGE statement to modify the data

The MERGE statement is an advanced syntax of Oracle, which can operate INSERT, UPDATE and DELETE combine together. The following functions can be achieved using the MERGE statement:

1) Copy data from one table to another (INSERT)

2) Use existing data to update the data in the table ( UPDATE)

3) Delete data from the table (DELETE)

The MERGE statement usually requires that there is some kind of relationship between the two tables, such as a relationship based on a primary key. The following is an example of using the MERGE statement to copy data from one table to another:

MERGE INTO target_table t
USING source_table s
ON (t.id = s.id)
WHEN MATCHED THEN
UPDATE SET t.name = s.name, t.age = s.age
WHEN NOT MATCHED THEN
INSERT (id, name, age)
VALUES (s.id, s.name, s.age);

In the above example, target_table represents the target table and source_table represents the source table. The MERGE statement matches based on the id field between the two tables. When the match is successful, the name and age fields in the source table are updated to the target table. When the match fails, the id, name, and age fields are copied from the source table to the target table.

3. Use subqueries to update data

Using subqueries to update data is a more flexible method and is very useful when you need to obtain data from different tables. An example is as follows:

UPDATE employee
SET salary = (
  SELECT salary
  FROM salary_history
  WHERE employee_id = employee.id
  AND pay_date = (
    SELECT MAX(pay_date)
    FROM salary_history
    WHERE employee_id = employee.id
  )
);

In the above example, there is a foreign key employee_id between the employee table and the salary_history table. The UPDATE statement uses a subquery to obtain the latest salary record from the salary_history table, and then updates the salary information of the record to the employee table.

To sum up, the above are three common methods for modifying table data in Oracle, and they are suitable for different scenarios. In actual use, it is necessary to choose the appropriate method according to the specific situation, and be extra cautious when making modifications to ensure the accuracy and completeness of the data.

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