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tiflash: MySQL compatibility about decimal insert through jdbc #21679

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tiflash: MySQL compatibility about decimal insert through jdbc
ChangRui-Ryan Aug 28, 2025
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Update develop/dev-guide-sample-application-java-jdbc.md
hfxsd Aug 29, 2025
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Update develop/dev-guide-sample-application-java-jdbc.md
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13 changes: 12 additions & 1 deletion develop/dev-guide-sample-application-java-jdbc.md
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Expand Up @@ -310,6 +310,17 @@
- Reduce [boilerplate code](https://en.wikipedia.org/wiki/Boilerplate_code) for managing connections and transactions.
- Manipulate data with data objects instead of a number of SQL statements.

### MySQL compatibility

When you insert data into a `DECIMAL` column, if the number of decimal places exceeds the defined scale, MySQL performs a `TRUNCATE` operation and inserts the data successfully, regardless of how many extra decimal places there are.

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[vale] reported by reviewdog 🐶
[PingCAP.Ambiguous] Consider using a clearer word than 'many' because it may cause confusion.

Raw Output:
{"message": "[PingCAP.Ambiguous] Consider using a clearer word than 'many' because it may cause confusion.", "location": {"path": "develop/dev-guide-sample-application-java-jdbc.md", "range": {"start": {"line": 315, "column": 197}}}, "severity": "INFO"}

In TiDB v8.1.2 and earlier versions:

- If the number of decimal places exceeds the column's defined scale but does not exceed 72, TiDB also performs a `TRUNCATE` operation and inserts the data successfully.
- However, if the number of decimal places exceeds 72, the write operation fails and returns an error.

Starting from TiDB v8.1.3, TiDB's behavior aligns with that of MySQL: regardless of the number of excess decimal places, it performs a `TRUNCATE` operation and inserts the data successfully.

## Next steps

- Learn more usage of MySQL Connector/J from [the documentation of MySQL Connector/J](https://dev.mysql.com/doc/connector-j/en/).
Expand All @@ -329,4 +340,4 @@

Ask the community on [Discord](https://discord.gg/DQZ2dy3cuc?utm_source=doc) or [Slack](https://slack.tidb.io/invite?team=tidb-community&channel=everyone&ref=pingcap-docs), or [submit a support ticket](https://tidb.support.pingcap.com/).

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