select-or-insert
时间: 2023-10-25 09:08:30 浏览: 37
"Select-or-insert" 是一种常见的数据库操作,它可以在数据库中查找一条记录,如果存在则返回该记录,如果不存在则插入一条新记录并返回该记录。这种操作通常用于保证数据库中某些数据的唯一性,例如用户的唯一标识、商品的唯一编码等。具体实现方式可以使用 SQL 语句的 "INSERT INTO ... ON DUPLICATE KEY UPDATE" 或者是数据库的事务操作来实现。
相关问题
mybatis-plus .or
在MyBatis-Plus中,.or()方法用于在条件构造器中使用or连接条件。当我们需要在查询条件中使用or时,可以通过调用.or()方法来实现。例如,使用.eq("id",1).or().eq("name","老王")表示查询id等于1或者name等于"老王"的记录。\[3\]这样的查询语句会生成类似于"select * from user where id = 1 or name = '老王'"的SQL语句。
#### 引用[.reference_title]
- *1* [Mybatis-Plus中and()和or()的使用与原理详解](https://blog.csdn.net/gb4215287/article/details/127420644)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v91^insertT0,239^v3^insert_chatgpt"}} ] [.reference_item]
- *2* [Mybatis-Plus使用或“or”问题,及使用方法](https://blog.csdn.net/Ying_ph/article/details/126262500)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v91^insertT0,239^v3^insert_chatgpt"}} ] [.reference_item]
- *3* [MyBatisplus or使用](https://blog.csdn.net/weixin_43932663/article/details/121078402)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v91^insertT0,239^v3^insert_chatgpt"}} ] [.reference_item]
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insert into select
The INSERT INTO SELECT statement in SQL is used to insert data into a table from another table or a query result set. The syntax for the INSERT INTO SELECT statement is as follows:
```
INSERT INTO table_name (column1, column2, ..., columnN)
SELECT column1, column2, ..., columnN
FROM source_table;
```
Where table_name is the name of the table where the data is being inserted, column1, column2, ..., columnN are the column names of the table, and source_table is the name of the table or query result set from where the data is being selected.
For example, if we have a table called "employees" with columns "employee_id", "employee_name", and "salary", and we want to insert data into a new table called "high_paid_employees" with only the "employee_id" and "salary" columns, for employees with a salary greater than $100,000, we can use the following query:
```
INSERT INTO high_paid_employees (employee_id, salary)
SELECT employee_id, salary
FROM employees
WHERE salary > 100000;
```
This query will insert the "employee_id" and "salary" columns of all employees with a salary greater than $100,000 from the "employees" table into the "high_paid_employees" table.