FlyingZC opened a new issue, #27043:
URL: https://github.com/apache/shardingsphere/issues/27043

   # Background
   Hi community,
   This issue is for #26878.
   
   ShardingSphere parser engine helps users parse a SQL to get the AST 
(Abstract Syntax Tree) and visit this tree to get SQLStatement (Java Object). 
Currently, we are planning to enhance the support for Oracle SQL parsing in 
ShardingSphere.
   
   More details:
   
https://shardingsphere.apache.org/document/current/en/reference/sharding/parse/
   
   # Task
   This issue is to support more oracle sql parse, as follows:
   ```sql
   CREATE MATERIALIZED VIEW hr.employees
     AS SELECT * FROM [email protected];
   ```
   
   ```sql
   CREATE MATERIALIZED VIEW hr.employees REFRESH FAST FOR UPDATE AS
     SELECT * FROM hr.employees@reg_uk.example.com e
       WHERE EXISTS
         (SELECT * FROM hr.departments@reg_uk.example.com d
          WHERE e.department_id = d.department_id
          AND EXISTS
            (SELECT * FROM hr.locations@reg_uk.example.com l
             WHERE l.city = 'London'
             AND d.location_id = l.location_id));
   ```
   
   ```sql
   CREATE MATERIALIZED VIEW hr.mview_employees AS
     SELECT employees.employee_id, employees.email 
     FROM [email protected]
   UNION ALL
     SELECT new_employees.employee_id, new_employees.email 
     FROM [email protected];
   ```
   
   ```sql
   CREATE MATERIALIZED VIEW oe.orders REFRESH FAST AS
    SELECT * FROM [email protected] o
    WHERE EXISTS
      (SELECT * FROM [email protected] c
       WHERE o.customer_id = c.customer_id AND c.credit_limit > 10000);
   ```
   
   ```sql
   CREATE MATERIALIZED VIEW join_sales_time_product_mv
   ENABLE QUERY REWRITE AS
   SELECT p.prod_id, p.prod_name, t.time_id, t.week_ending_day,
          s.channel_id, s.promo_id, s.cust_id, s.amount_sold
   FROM   sales s, products p, times t
   WHERE  s.time_id=t.time_id  AND s.prod_id = p.prod_id;
   ```
   
   # Process
   1. First confirm that this is a correct oracle sql syntax, if not please 
ignore;
   2. Compare SQL definitions in Oficial SQL Doc and ShardingSphere SQL Doc;
   3. If there is any difference in ShardingSphere SQL Doc, please correct them 
by referring to the Official SQL Doc;
   4. Run mvn install the current_file_module;
   5. Check whether there are any exceptions. If indeed, please fix them. 
(Especially xxxVisitor.class);
   6. Add new corresponding SQL case in SQL Cases and expected parsed result in 
Expected Statment XML;
   7. Run SQLParserParameterizedTest to make sure no exceptions.
   
   # Relevant Skills
   1. Master JAVA language
   2. Have a basic understanding of Antlr `g4` file
   3. Be familiar with Oracle SQLs


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