FlyingZC opened a new issue, #27075:
URL: https://github.com/apache/shardingsphere/issues/27075

   # 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 OR REPLACE VIEW edge_time AS
   SELECT 
     (CASE
        WHEN ((GROUPING(calendar_year)=0 )
          AND (GROUPING(calendar_quarter_desc)=1 ))
          THEN (TO_CHAR(calendar_year) || '_0')
        WHEN ((GROUPING(calendar_quarter_desc)=0 )
          AND (GROUPING(calendar_month_desc)=1 ))
          THEN (TO_CHAR(calendar_quarter_desc) || '_1')
        WHEN ((GROUPING(calendar_month_desc)=0 )
          AND (GROUPING(time_id)=1 ))
          THEN (TO_CHAR(calendar_month_desc) || '_2')
        ELSE (TO_CHAR(time_id) || '_3')
      END) Hierarchical_Time,
      calendar_year yr, calendar_quarter_number qtr_num,
      calendar_quarter_desc qtr, calendar_month_number mon_num,
      calendar_month_desc mon, time_id - TRUNC(time_id, 'YEAR') + 1 day_num,
      time_id day,
   GROUPING_ID(calendar_year, calendar_quarter_desc,
     calendar_month_desc, time_id) gid_t
   FROM TIMES
   GROUP BY ROLLUP
    (calendar_year, (calendar_quarter_desc, calendar_quarter_number),
    (calendar_month_desc, calendar_month_number), time_id);
   ```
   
   ```sql
   CREATE OR REPLACE VIEW Library_view AS
     SELECT i.Section, CAST (
       MULTISET (
         SELECT b.Booknum, b.Title, b.Author, b.Available
         FROM Book_table b
         WHERE b.Section = i.Section
       ) AS Book_list_t
     ) BOOKLIST
     FROM Library_table i;
   ```
   
   ```sql
   CREATE OR REPLACE VIEW emp_simple_xml OF XMLType
     XMLSCHEMA "http://www.oracle.com/emp_simple.xsd"; ELEMENT "Employee"
      WITH OBJECT ID (XMLCast(XMLQuery('/Employee/EmployeeId/text()'
                                       PASSING OBJECT_VALUE
                                       RETURNING CONTENT)
                              AS BINARY_DOUBLE)) AS
      SELECT
        XMLElement("Employee",
                   XMLAttributes(
                     'http://www.oracle.com/emp_simple.xsd' AS "xmlns" ,
                     'http://www.w3.org/2001/XMLSchema-instance' AS "xmlns:xsi",
                     'http://www.oracle.com/emp_simple.xsd
                      http://www.oracle.com/emp_simple.xsd'
                     AS "xsi:schemaLocation"),
                   XMLForest(e.employee_id    AS "EmployeeId",
                             e.last_name      AS "Name",
                             e.job_id         AS "Job",
                             e.manager_id     AS "Manager",
                             e.hire_date      AS "HireDate",
                             e.salary         AS "Salary",
                             e.commission_pct AS "Commission",
                             XMLForest(
                               d.department_id   AS "DeptNo",
                               d.department_name AS "DeptName",
                               d.location_id     AS "Location") AS "Dept"))
        FROM employees e, departments d
        WHERE e.department_id = d.department_id;
   ```
   
   ```sql
   CREATE OR REPLACE VIEW emp_view OF emp_t WITH OBJECT IDENTIFIER(empno)
      AS SELECT e.empno, e.empname, e.salary, 
                         MAKE_REF(dept_view, e.deptno) 
            FROM emp e;
   ```
   
   ```sql
   CREATE OR REPLACE VIEW cube_prod_time AS
   SELECT 
     (CASE
        WHEN ((GROUPING(calendar_year)=0 ) 
          AND (GROUPING(calendar_quarter_desc)=1 ))
          THEN (TO_CHAR(calendar_year) || '_0')
        WHEN ((GROUPING(calendar_quarter_desc)=0 )
          AND (GROUPING(calendar_month_desc)=1 ))
          THEN (TO_CHAR(calendar_quarter_desc) || '_1')
        WHEN ((GROUPING(calendar_month_desc)=0 )
          AND (GROUPING(t.time_id)=1 ))
          THEN (TO_CHAR(calendar_month_desc) || '_2')
        ELSE (TO_CHAR(t.time_id) || '_3')
     END) Hierarchical_Time,
     calendar_year year, calendar_quarter_desc quarter,
     calendar_month_desc month, t.time_id day,
     prod_category cat, prod_subcategory subcat, p.prod_id prod,
     GROUPING_ID(prod_category, prod_subcategory, p.prod_id,
       calendar_year, calendar_quarter_desc, calendar_month_desc,t.time_id) gid,
     GROUPING_ID(prod_category, prod_subcategory, p.prod_id) gid_p,
     GROUPING_ID(calendar_year, calendar_quarter_desc,
       calendar_month_desc, t.time_id) gid_t,
     SUM(amount_sold) s_sold, COUNT(amount_sold) c_sold, COUNT(*) cnt
   FROM SALES s, TIMES t, PRODUCTS p
   WHERE s.time_id = t.time_id AND
     p.prod_name IN ('Bounce', 'Y Box') AND s.prod_id = p.prod_id
   GROUP BY
     ROLLUP(calendar_year, calendar_quarter_desc, calendar_month_desc, 
t.time_id),
     ROLLUP(prod_category, prod_subcategory, 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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