FlyingZC opened a new issue, #27153:
URL: https://github.com/apache/shardingsphere/issues/27153

   # 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
   MERGE 
   USING Product_Changes S                      -- Source/Delta table 
   INTO Products P                              -- Destination table 1 
   ON (P.PROD_ID = S.PROD_ID)                   -- Search/Join condition 
   WHEN MATCHED THEN 
   UPDATE                                       -- update if join 
   SET P.PROD_LIST_PRICE = S.PROD_NEW_PRICE 
   WHERE P.PROD_STATUS <> "OBSOLETE"            -- Conditional UPDATE
   ```
   
   ```sql
   MERGE USING New_Product S           -- Source/Delta table
   INTO Products D2                    -- Destination table 2
   ON (D2.PROD_ID = S.PROD_ID)         -- Search/Join condition
   WHEN NOT MATCHED THEN               -- insert if no join
   INSERT (PROD_ID, PROD_STATUS) VALUES (S.PROD_ID, S.PROD_NEW_STATUS)
   ```
   
   ```sql
   MERGE USING New_Product S       -- Source/Delta table 
   INTO Products P                 -- Destination table 1 
   ON (1 = 0)                      -- Search/Join condition 
   WHEN NOT MATCHED THEN           -- insert if no join 
   INSERT (PROD_ID, PROD_STATUS) VALUES (S.PROD_ID, S.PROD_NEW_STATUS)
   ```
   
   ```sql
   MERGE USING Product_Changes S
   INTO Products D ON (D.PROD_ID = S.PROD_ID)
   WHEN MATCHED THEN
   UPDATE SET D.PROD_LIST_PRICE =S.PROD_NEW_PRICE, D.PROD_STATUS = 
S.PROD_NEWSTATUS
   DELETE WHERE (D.PROD_STATUS = "OBSOLETE")
   WHEN NOT MATCHED THEN
   INSERT (PROD_ID, PROD_LIST_PRICE, PROD_STATUS)
   VALUES (S.PROD_ID, S.PROD_NEW_PRICE, S.PROD_NEW_STATUS);
   ```
   
   ```sql
   MERGE USING Product_Changes S                      -- Source/Delta table
   INTO Products P                                    -- Destination table 1
   ON (P.PROD_ID = S.PROD_ID)                         -- Search/Join condition
   WHEN MATCHED THEN UPDATE                           -- update if join
   SET P.PROD_LIST_PRICE = S.PROD_NEW_PRICE
   WHERE P.PROD_STATUS <> "OBSOLETE"                  -- Conditional
   WHEN NOT MATCHED THEN
   INSERT (PROD_ID, PROD_STATUS, PROD_LIST_PRICE)     -- insert if not join
   VALUES (S.PROD_ID, S.PROD_NEW_STATUS, S.PROD_NEW_PRICE)
   WHERE S.PROD_STATUS <> "OBSOLETE";
   ```
   
   # 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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