SHOW DATABASES & SHOW TABLES parse conflict with Oracle DatabaseType

[strongduanmu]

Bug Report

Which version of ShardingSphere did you use?

9462a44

Which project did you use? ShardingSphere-JDBC or ShardingSphere-Proxy?

ShardingSphere-Proxy

Expected behavior

When I parse SHOW DATABASES and SHOW TABLES with Oracle databaseType, it should not supported exception.

Actual behavior

Parse correctly.

Reason analyze (If you can)

systemVariable sytax in Oracle DALStatement.g4 is too loose. According to Oracle doc - https://docs.oracle.com/en/database/oracle/oracle-database/23/sqpug/SET-system-variable-summary.html#GUID-A6A5ADFF-4119-4BA4-A13E-BC8D29166FAE, systemVariable should only support system variables SET by the SET statement, not generic identifiers.

Steps to reproduce the behavior, such as: SQL to execute, sharding rule configuration, when exception occur etc.

Example codes for reproduce this issue (such as a github link).

[github-actions]

There hasn't been any activity on this issue recently, and in order to prioritize active issues, it will be marked as stale.