FlyingZC opened a new issue, #27111:
URL: https://github.com/apache/shardingsphere/issues/27111

   # 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 TABLE tab AS SELECT DBMS_LOB.SUBSTR(clob_col) from tab@dbs2;
   ```
   
   ```sql
   CREATE TABLE temp_sales_step1_invalid NOLOGGING PARALLEL AS
   SELECT * FROM temp_sales_step1 s
   WHERE NOT EXISTS (SELECT 1 FROM product p WHERE p.upc_code=s.upc_code);
   ```
   
   ```sql
   CREATE TABLE temp_sales_step2 NOLOGGING PARALLEL AS
   SELECT sales_transaction_id, product.product_id sales_product_id,
      sales_customer_id, sales_time_id, sales_channel_id, sales_quantity_sold,
      sales_dollar_amount
   FROM  temp_sales_step1, product
   WHERE temp_sales_step1.upc_code = product.upc_code (+);
   ```
   
   ```sql
   CREATE TABLE temp_sales_step2 NOLOGGING PARALLEL AS SELECT 
sales_transaction_id,
     product.product_id sales_product_id, sales_customer_id, sales_time_id,
     sales_channel_id, sales_quantity_sold, sales_dollar_amount
   FROM  temp_sales_step1, product
   WHERE temp_sales_step1.upc_code = product.upc_code;
   ```
   
   ```sql
   CREATE TABLE temporary 
      (employee_id, start_date, end_date, job_id, dept_id) 
   AS SELECT 
        employee_id, start_date, end_date, job_id, department_id
   FROM job_history; 
   
   DROP TABLE job_history; 
   
   RENAME temporary TO job_history;
   ```
   
   # 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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