How to modify records in oracle

Oracle database is a relational database management system widely used in enterprise-level applications. It is one of the most popular databases on the market today. In daily business operations, it is often necessary to modify database records, so it is very important to understand the modification process of Oracle database records. This article will introduce the relevant knowledge of Oracle modification records.

First, we need to understand the basic structure of the Oracle database. Oracle database contains multiple tables (Table), each table contains multiple columns (Column), and each column contains multiple rows (Row). When processing business data, we need to modify the rows in the table, but it should be noted that each row in the table has a unique identifier. This identifier is called the row ID (Row ID), which is composed of Automatically generated by the Oracle database system.

So how do we modify the records in the table? Oracle database provides multiple ways to modify records, two of which will be introduced in detail here.

1. Use the UPDATE command

The UPDATE command is one of the most commonly used ways to modify records in the Oracle database. It can achieve single or multiple modifications to specific rows in the table. column to modify. The basic syntax is as follows:

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

Among them, table_name represents the name of the table to be modified, column1, column2, etc. represent the names of the columns to be modified, value1, value2, etc. represent the values ​​of the columns to be modified, and condition represents modification. condition. The sample code is as follows:

UPDATE employees
SET salary = 5000, department = 'sales'
WHERE employee_id = 1001;

The above code indicates that the value of the salary column of the row with employee_id 1001 in the employees table is modified to 5000, and the value of the department column is modified to sales.

When using the UPDATE command to modify records, you need to pay attention to the following points:

• You need to lock the table before modifying records to avoid data corruption caused by multiple users modifying operations at the same time. Inconsistency.
• When modifying records, you need to pay special attention to the conditions in the WHERE clause. If the conditions are incorrect, it will cause modification errors or even modify the records of the entire table.
• When modifying records, you need to pay attention to the atomicity of the transaction, and you need to pay special attention to the situation of distributed transactions.

2. Use the MERGE command

The MERGE command is one of the latest ways to modify records in the Oracle database. It can merge or add two tables Record. The basic syntax is as follows:

MERGE INTO table_name1
USING table_name2
ON (condition)
WHEN MATCHED THEN
    UPDATE SET column1 = value1, column2 = value2, ...
WHEN NOT MATCHED THEN 
    INSERT (column1, column2, ...) VALUES (value1, value2, ...);

Among them, table_name1 represents the target table to be merged or added, table_name2 represents the source table to be merged or added, and condition represents the condition for merging or adding. When the records in the source table and the target table match, use the UPDATE clause to update the records in the target table. When the records in the source table and the target table do not match, use the INSERT clause to add new records to the target table.

The sample code is as follows:

MERGE INTO orders o
USING temp_orders t
ON (o.order_id = t.order_id)
WHEN MATCHED THEN
    UPDATE SET o.order_status = t.order_status, o.order_amount = t.order_amount
WHEN NOT MATCHED THEN
    INSERT (order_id, order_status, order_amount) VALUES (t.order_id, t.order_status, t.order_amount);

The above code represents merging the records in the temp_orders table into the orders table. When the order_id is the same, the order_status and order_amount columns in the orders table are updated; when the order_id is different, the values ​​of the order_id, order_status and order_amount columns in the temp_orders table are inserted into the orders table.

Like the UPDATE command, when using the MERGE command to modify records, you also need to pay special attention to the atomicity of the transaction. Special attention needs to be paid to the situation of distributed transactions.

Summary:

This article introduces how to use the UPDATE and MERGE commands to modify records in the Oracle database. It should be noted that before performing modification operations, the table needs to be locked to prevent multiple users from concurrently modifying the same record. At the same time, attention must be paid to the atomicity of the transaction. In addition to the two methods introduced in this article, Oracle database also provides other ways to modify records, such as using PL/SQL stored procedures, etc. Readers can choose according to specific needs.

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