Question

我无法使我的sql case表达式起作用。当我使用此sql语句时，它可以正常工作：

  SELECT
    TimeInt AS time,
    oV101DirectionA,
    oV101DirectionB,
    id
  FROM
    machine_data
  WHERE
    id%1=0 AND
    machine_id = 3 AND
    $__unixEpochFilter(TimeInt) = TRUE
    GROUP BY DATE_FORMAT(TimeStr, '%Y%m%d%k%i')
  ORDER BY TimeInt ASC

但是当我修改代码以更好地缩放时，则不会显示任何数据，这也不是错误。如果两个日期之间的时间窗口（以秒为单位）相距甚远，则应跳过数据库中的行以获得更好的性能。

  SELECT
    TimeInt AS time,
    oV101DirectionA,
    oV101DirectionB,
    id
  FROM
    machine_data
  WHERE
    CASE WHEN ($__unixEpochTo(TimeInt)-$__unixEpochFrom(TimeInt)) > 100 THEN 'id%10 = 0'
        WHEN ($__unixEpochTo(TimeInt)-$__unixEpochFrom(TimeInt)) > 1000 THEN 'id%100 = 0'
    ELSE 'id%1 = 0'
    END AND
    machine_id = 3 AND
    $__unixEpochFilter(TimeInt) = TRUE
    GROUP BY DATE_FORMAT(TimeStr, '%Y%m%d%k%i')
  ORDER BY TimeInt ASC

我已经在线阅读了很多有关sql中的case语句的信息，但是找不到针对我特定问题的答案。

Answer 1

我怀疑这就是您想要的：

public function onKernelException(GetResponseForExceptionEvent $event)
{
    // how to know if $event this happened after/during kernel.terminate?
}

Answer 2

您不能以这种方式使用bool operator <(Employee const & lhs, Employee const & rhs) { return lhs.combined_name() < rhs.combined_name(); } // a.k.a. std::swap void swap(Employee & lhs, Employee & rhs) { Employee temp(static_cast<Employee&&>(lhs)); // a.k.a. std::move lhs = static_cast<Employee&&>(rhs); rhs = static_cast<Employee&&>(temp); } void bubble_sort_impl(Employee * begin, Employee * end) { for (; end != begin; --end) { for (Employee * it = begin; it+1 != end; ++it) { if (*(it+1) < *it) { swap(*it, *(it+1)); } } } } // do we really need "bubble_" or "_address_book" in this name? void AddressBook::bubble_sort_address_book() { bubble_sort_impl(employees, employees + noOfEmployees); }表达式，因为它的输出是 value ，而不是逻辑条件。但是我们可以将您的CASE逻辑改写为：

WHERE

SQL案例表达式在grafana中无法正常工作

2 个答案: