????jdbc connector????????

[claylin]

hi 
all????????????????????sql????????????clickhouse??????????????????????????????????https://github.com/apache/flink/blob/d04872d2c6b7570ea3ba02f8fc4fca02daa96118/flink-connectors/flink-connector-jdbc/src/main/java/org/apache/flink/connector/jdbc/dialect/JdbcDialects.java#L30,
 
??????????????????????DerbyDialect??MySQLDialect??PostgresDialect??????????????????????jdbc????????????????SQL??????????????????????????????????????????????