如何在Django中实现MYSQL的TIMESTAMPDIFF（）

Question

如何在Django中实现MYSQL的TIMESTAMPDIFF(UNIT,EXPR_1,EXPR_2)（作为DB函数）？

Answer 1

我在这里How to annotate a difference of datetime in days回答了类似的问题。

from django.db.models.functions import Func


class TimeStampDiff(Func):
    class PrettyStringFormatting(dict):
        def __missing__(self, key):
            return '%(' + key + ')s'

    def __init__(self, *expressions, **extra):
        unit = extra.pop('unit', 'day')
        self.template = self.template % self.PrettyStringFormatting({"unit": unit})
        super().__init__(*expressions, **extra)

    function = 'TIMESTAMPDIFF'
    template = "%(function)s(%(unit)s, %(expressions)s)"

用法

TimeStampDiff(expr_1,expr_2,unit=valid_unit)