FlyingZC opened a new issue, #27026:
URL: https://github.com/apache/shardingsphere/issues/27026

   # 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 FUNCTION Power_GreaterThanAny_Func(
     object PowerDemand_Typ, value NUMBER)
   RETURN NUMBER AS
      idx NUMBER;
     BEGIN
       FOR idx IN object.CellDemandValues.FIRST..object.CellDemandValues.LAST 
LOOP
         IF (object.CellDemandValues(idx) > value) THEN
      RETURN 1;
         END IF;
       END LOOP;
      RETURN 0;
     END;
   ```
   
   ```sql
   CREATE FUNCTION eq_f(a VARCHAR2, b VARCHAR2) RETURN NUMBER AS
   BEGIN
      IF a = b THEN RETURN 1;
      ELSE RETURN 0;
      END IF;
   END;
   ```
   
   ```sql
   CREATE FUNCTION Power_LessThanSpecific_Func(
     object PowerDemand_Typ, cell NUMBER, value NUMBER)
   RETURN NUMBER AS
     BEGIN
     IF cell <= object.CellDemandValues.LAST
     THEN
        IF (object.CellDemandValues(cell) < value) THEN
      RETURN 1;
        ELSE
      RETURN 0;
        END IF;
     ELSE
        RETURN NULL;
     END IF;
     END;
   ```
   
   ```sql
   CREATE FUNCTION func1 (sch VARCHAR2 , obj VARCHAR2 )
   RETURN VARCHAR2(100);
   BEGIN
   RETURN 'language_id = SYS_CONTEXT(''userenv'', ''LANG'')';
   END
   ```
   
   ```sql
   CREATE FUNCTION SecondMax (input NUMBER) RETURN NUMBER
       PARALLEL_ENABLE AGGREGATE USING SecondMaxImpl;
   ```
   
   # 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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