sql-mode compatibility docs are out of date

[wwar]

Change Request

This repository is ONLY used to solve issues related to DOCS.
For other issues (related to TiDB, PD, etc), please move to other repositories.

Please answer the following questions before submitting your issue. Thanks!

1. Describe what you find is inappropriate or missing in the existing docs.

On https://pingcap.com/docs/stable/reference/mysql-compatibility/#sql-modes it says that ORACLE, POSTGRESQL etc are not supported.

But on https://pingcap.com/docs/stable/reference/sql/sql-mode/ it says that these modes are fully supported.

I did a quick test, and it looks like the are now fully supported:

mysql> set sql_mode='oracle';
Query OK, 0 rows affected (0.00 sec)

mysql> select @@sql_mode;
+----------------------------------------------------------------------------------------------------------------------+
| @@sql_mode                                                                                                           |
+----------------------------------------------------------------------------------------------------------------------+
| PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE,NO_KEY_OPTIONS,NO_TABLE_OPTIONS,NO_FIELD_OPTIONS,NO_AUTO_CREATE_USER,ORACLE |
+----------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

2. Describe your suggestion or addition.

Update compatibility docs.

3. Provide some reference materials (documents, websites, etc) if you could.

[XuHuaiyu]

@wwar Thanks. For the SQL Modes which are deprecated in MySQL 5.7 and removed in MySQL 8.0, TiDB only supports the syntax of them but not the functionality.

@TomShawn We may update the doc to specify this.