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**Description**

A sql sensor which uses Standard SQL due to default one uses legacy sql


**Use case / motivation**

Currently (correct me if I am wrong!), the sql sensor only supports legacy sql. If I want to poke a BQ table, I do not think I can do that using standard sql right now.


**Are you willing to submit a PR?**

If community approves of this idea, sure!


airflow/sensors/sql.py
hook = self._get_hook()
        self.log.info('Poking: %s (with parameters %s)', self.sql, self.parameters)
        records = hook.get_records(self.sql, self.parameters)
        if not records:
            if self.fail_on_empty:
                raise AirflowException("No rows returned, raising as per fail_on_empty flag")
            else:
                return False
        first_cell = records[0][0]
        if self.failure is not None:
            if callable(self.failure):
                if self.failure(first_cell):
                    raise AirflowException(f"Failure criteria met. self.failure({first_cell}) returned True")
            else:
                raise AirflowException(f"self.failure is present, but not callable -> {self.failure}")
        if self.success is not None:
            if callable(self.success):
                return self.success(first_cell)
            else:
                raise AirflowException(f"self.success is present, but not callable -> {self.success}")
        return bool(first_cell)