MySQL查找双精度的最小值/最大值 [英] MySQL Finding min/max values for double
问题描述
相关的MySQL文档指出：对于双打：
允许的值是-1.7976931348623157E + 308至-2.22507385850720142014E-308、0和2.2250738585072014E-308至1.7976931348623157E +308。
Permissible values are -1.7976931348623157E+308 to -2.2250738585072014E-308, 0, and 2.2250738585072014E-308 to 1.7976931348623157E+308.
和
这些是基于IEEE标准的理论限制。实际范围可能会略小，具体取决于您的硬件或操作系统。
These are the theoretical limits, based on the IEEE standard. The actual range might be slightly smaller depending on your hardware or operating system.
我发现系统上的实际范围实际上较小！是否有SQL查询或其他方法可以找出双精度的实际最小值和最大值是什么？
I'm finding that the actual range is actually smaller on my system! Is there a SQL query or some other way to find out what the actual minimum and maximum values are for a double?
推荐答案
如果您想找到并证明您知道系统上的确切最大值，这是在几分钟的执行时间内完成该操作的一种方法。
If you want to find and prove you know the exact max value on a system, here is a way to do it in a few minutes of execution time.
执行一个简单的循环以1开头的值并将其插入。在每个循环中，将值乘以10，直到溢出失败。最后，您将获得minWorkingValue和maxFailedValue。
Do a simple loop that starts with the value of 1 and inserts it. On each loop multiple the value by 10 until it fails on overflow. At the end of this you have the minWorkingValue and the maxFailedValue.
现在执行第二个循环，在minWorkingValue和maxFailedValue之间插入一个值。如果成功，它将成为新的minWorkingValue。如果失败，它将成为新的maxFailedValue。继续直到maxFailedValue-minWorkingValue =1。最后，minWorkingValue是您可以插入的实际最大值。
Now do a second loop that inserts a value halfway between minWorkingValue and maxFailedValue. If it succeeds it becomes the new minWorkingValue. If it fails it becomes the new maxFailedValue. Continue until maxFailedValue - minWorkingValue = 1. At the end minWorkingValue is your actual max value you can insert.
或者，如果您非常确定知道这些值的位置，可能是，然后跳过第一步，手动设置minWorkingValue和maxFailedValue并直接进入第二个循环。
As an alternative, if you are pretty sure you know where these values might be, then skip the first step and manually set minWorkingValue and maxFailedValue and straight to the 2nd loop.
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