Mysql没有选择空值

Question

我有以下查询：

SELECT * FROM table 
WHERE orderdate >= "2015-12-01" 
    AND orderdate <= "2015-12-31" 
    AND values > 0 
    AND orders <> 'Returned'

问题是查询没有返回orders列为NULL的行，我无法弄清楚原因。

Answer 1

这是sql语言。 Mysql不会将NULL视为值。因此，如果要包含NULL，我们必须指定。

// Get all instances of Chrome running on the local computer.
// This will return an empty array if Chrome isn't running.
array<Process^>^localByName = Process::GetProcessesByName("chrome");

// Print out each individual processes Process Name, ID, and Window Title
for each (Process^ p in localByName)
{
    Console::WriteLine("Process: {0} ID: {1}, Main window title: {2} ", p->ProcessName, p->Id, p->MainWindowTitle);
}