从表中的datetime列中选择不同的日期

I have a table

我有一张桌子

id | message | date_posted
1  | testing | 2011-03-08 03:15:13
2  | testing | 2011-03-06 03:15:13
3  | testing | 2011-03-08 03:15:13

And need a query where I return a list of distinct dates in desc order. I tried to formulate a query like so

并且需要一个查询,其中我以desc顺序返回不同日期的列表。我试图像这样制定一个查询

SELECT DISTINCT CAST(`date_posted` AS DATE) AS dateonly FROM table

This gives me dates but they're not distinct and have duplicates.

这给了我约会,但它们并不明显,并且有重复。

Any ideas? (Using php/mysql)

有任何想法吗? (使用php / mysql)

MAJOR EDIT:

Forgot an important piece of information. I'm trying to get unique dates based on month and year.

忘了重要的一条信息。我正在尝试根据月份和年份获得独特的日期。

2011-03-08 03:15:13
2011-03-06 03:15:13
2011-03-02 03:15:13
2011-03-01 03:15:13
2011-02-01 03:15:13

So running the query would only return [2011-03-dd,2011-02-01] (dd being any day)

所以运行查询只会返回[2011-03-dd,2011-02-01](dd是任何一天)

Apologize for not stating this.

为没有说明这一点而道歉。

4 个解决方案

#1

Your query will return unique DATES, as you've specified. If you want to get just unique MONTHS/YEARS, you should either modify you dates in a way, that each date becomes the first day of the month, or you should just go with some string representation like 'YYYY-MM'. Sorry, I can't write you an exact code how to do this, as I do not develop on mysql, but I think this should get you somewhere :)

您的查询将返回您指定的唯一日期。如果你想获得唯一的MONTHS / YEARS,你应该以某种方式修改你的日期,每个日期成为一个月的第一天,或者你应该使用像'YYYY-MM'这样的字符串表示。对不起,我不能给你一个确切的代码如何做到这一点,因为我没有在mysql上开发,但我认为这应该让你在某处:)

SELECT DISTINCT YEAR(date_posted), MONTH(date_posted) FROM table

#2

SELECT DATE(`date_posted`) AS dateonly 
FROM   table 
GROUP  BY DATE(`date_posted`)

#3

Working example

create table dts (dt datetime);
insert dts select '2011-03-08 03:15:13';
insert dts select '2011-03-07 03:15:13';
insert dts select '2011-03-09 03:15:13';
insert dts select '2011-03-08 03:15:13';

select distinct cast(dt as date) from dts;

Output

"cast(dt as date)"
"2011-03-08"
"2011-03-07"
"2011-03-09"

Query for distinct Year-Month

查询不同的年月

select date(date_format(dt, '%Y-%m-1')) as dt
from dts
group by dt;

Output (the result is a date column, with the day set to '1')

输出(结果是日期列,日期设置为'1')

2011-03-01

#4

SELECT DISTINCT date(date_format(COLUMN_NAME, '%Y-%m-%d')) as uniquedates from TABLE_NAME

#1

SELECT DISTINCT YEAR(date_posted), MONTH(date_posted) FROM table

#2

SELECT DATE(`date_posted`) AS dateonly 
FROM   table 
GROUP  BY DATE(`date_posted`)

#3