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tiflash: MySQL compatibility about decimal insert through jdbc #20786

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tiflash: MySQL compatibility about decimal insert through jdbc
ChangRui-Ryan Aug 15, 2025
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Update develop/dev-guide-sample-application-java-jdbc.md
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Expand Up @@ -280,6 +280,17 @@ Java 驱动程序提供对数据库的底层访问，但要求开发者：
- 减少管理连接和事务的[模板代码](https://en.wikipedia.org/wiki/Boilerplate_code)
- 使用数据对象代替大量 SQL 语句来操作数据

### MySQL 兼容性

当写入 DECIMAL 类型的数据时，如果小数位数超过字段定义的小数位数，无论超过多少，MySQL 都会执行 `TRUNCATE` 并插入成功。

在 TiDB v8.1.2 及之前版本中：

- 如果小数位数超过字段定义的小数位数但未超过 72 位，同样会执行 `TRUNCATE` 并插入成功。
- 如果小数位数超过 72 位，写入会失败并报错。

从 TiDB v8.1.3 开始，TiDB 的行为和 MySQL 保持一致，即无论小数位数超过多少，都会执行 `TRUNCATE` 并插入成功。

## 下一步

- 关于 MySQL Connector/J 的更多使用方法，可以参考 [MySQL Connector/J 官方文档](https://dev.mysql.com/doc/connector-j/en/)。
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