在android sqlite数据库中比较日期（存储为字符串）？ [英] Compare dates (stored as string) in android sqlite database?

问题描述

我将数据库中的日期保存为 String ，格式如下：

I store dates as String in my database, in this format:

YYYY-MM-DD HH:MM:SS

这是支持的格式之一（< a href =http://www.sqlite.org/lang_datefunc.html> http://www.sqlite.org/lang_datefunc.html ）。现在我想将这些存储的日期（以及字符串）与另一个日期进行比较。我的日期存储在列 column_date 中，所以我正在尝试：

which is one of supported formats (http://www.sqlite.org/lang_datefunc.html). Now I want to compare these stored dates (well, strings) with another dates. My dates are stored in column column_date, so I'm trying this:

SELECT  * FROM MyTable
WHERE 
(Date(column_date) >= Date (2000-01-01) AND Datetime(column_date) <= Datetime (2050-01-01))

当我阅读文档时，日期和时间函数使用IS0-8601的一个子集日期和时间格式。 date（）函数返回以下格式的日期：YYYY-MM-DD。所以我想，我做的正确 - 我从存储的字符串创建日期，并将其与从另一个创建的日期进行比较字符串。

As i read documentation, The date and time functions use a subset of IS0-8601 date and time formats. The date() function returns the date in this format: YYYY-MM-DD. so I suppose, I'm doing it right - I create date from stored string and compare it with date created from another strings.

但它不起作用，即使 column_date 是今年的日期，您可以看到开始和结束日期非常仁慈。尝试这个（使用datetime而不是日期）：

But it doesn't work, even when column_date is date from this year, and as u can see the start and end dates are very benevolent. Tried also this (used datetime instead of date):

SELECT  * FROM MyTable
    WHERE 
    (datetime(column_date) >= Date (2000-01-01) AND datetime(column_date) <= Datetime (2050-01-01))

这个（使用而不是< =和> =）

and this (use between instead of <= and >=)

SELECT  * FROM MyTable
    WHERE 
    (Date(column_date) between Date (2000-01-01) AND Datetime (2050-01-01))

和所有其他可能的组合。我做错了什么，我很愚蠢，还是文件谎言，还是我错过了一些非常重要的东西？尝试找到解决方案几个小时，但没有任何工作...

and all other possible combinations. What the hell I'm doing wrong, am I stupid, or the documentaion lies, or I missed something very important? Trying to find solution few hours, but nothing works...

推荐答案

如果您将日期存储为格式

if you are storing dates as strings in the format

YYYY-MM-DD HH:mm:ss  

====>那么你的日期字段是一个DateTime数据类型

====> then your date field is a DateTime datatype

所以你必须使用这样的查询

Thus you have to use such query

select * 
  from MyTable 
  where mydate >= Datetime('2000-01-01 00:00:00') 
  and mydate <= Datetime('2050-01-01 23:00:59')

您也可以使用@Joop Eggen提供的代码与运算符之间的代码相同。

you can also use the snippet given by @Joop Eggen with th between operator it's th same approche.

BETWEEN 运算符在逻辑上等同于一对比较。 x BETWEEN y AND z等同于x> = y AND x <= z，除了使用BETWEEN，只能对x表达式进行一次评估。请参阅sqlite3 docs

The BETWEEN operator is logically equivalent to a pair of comparisons. "x BETWEEN y AND z" is equivalent to "x>=y AND x<=z" except that with BETWEEN, the x expression is only evaluated once. see sqlite3 docs

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