default String getRowExistsStatement(String tableName, String[] conditionFields) {
        String fieldExpressions = Arrays.stream(conditionFields)
                .map(f -> quoteIdentifier(f) + "=?")
                .collect(Collectors.joining(" AND "));
        return "SELECT 1 FROM " + quoteIdentifier(tableName) + " WHERE " + fieldExpressions;
    }
Get row exists statement by condition fields. Default use SELECT.
rdb/rdb-sink/src/main/java/com/dtstack/flink/sql/sink/rdb/dialect/JDBCDialect.java