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:

CHANGE DB_UNIQUE_NAME FROM BOSTON_A TO BOSTON_B;

CHECK ((A IS NULL AND B IS NULL AND C IS NULL) OR
       (A IS NOT NULL AND B IS NOT NULL AND C IS NOT NULL))

CASE WHEN expr1 IS NOT NULL THEN expr1 ELSE expr2 END

CHECK ((C1 IS NULL AND C2 IS NULL) OR (C1 IS NOT NULL AND C2 IS NOT NULL))

CHECK (column_name IS NOT NULL)

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