mysql datatype to store month and year only [closed]

Answer 1

As of 5.7 one could make use of generated columns, which lets you enforce year-month uniqueness while also using date functions on another field without breaking data integrity by duplicating:

CREATE TABLE `year_month` (
  `Year` int(11) NOT NULL,
  `Month` enum(
      'January',
      'February',
      'March',
      'April',
      'May',
      'June',
      'July',
      'August',
      'September',
      'October',
      'November',
      'December'
      ) NOT NULL,
  `GENERATED_YearMonth` date
      GENERATED ALWAYS AS
          ((makedate(`Year`,1) + interval (`Month` - 1) month))
      STORED,
  PRIMARY KEY (`Year`,`Month`),
  KEY `year_month_GENERATED_YearMonth_index` (`GENERATED_YearMonth`)
)
;

Answer 2

Why bother? Just store it as a complete date (perhaps always using the first as the day) and use the database functions MONTH() and YEAR() if you only need part of it. This makes using that field much easier as you can still do range queries, etc.

Answer 3

SELECT * FROM Users
WHERE 
    MONTH(DateTime) = '07'
AND 
    YEAR(DateTime) = '2015'
AND 
    DAY(DateTime) = '26'

you can filter like above but still if you want to store year/month and day as separate, its useless until you apply indexing and its very big data.

Answer 4

Another solution is to build generated columns from your DATETIME/DATE source.

ALTER TABLE stats 
ADD COLUMN year SMALLINT GENERATED ALWAYS AS (YEAR(stat_date)) NOT NULL,
ADD COLUMN month smallint GENERATED ALWAYS AS (MONTH(stat_date)) NOT NULL;

Background

I had a similar problem. After reading this thread, I decided to store incomplete dates (with zeros). It worked on older versions of MySQL, but newer versions produced "Incorrect date" error. As mentioned before, you can turn the error into warning using the NO_ZERO_IN_DATE setting. But the setting itself is deprecated. Hence, in the future, it would only be possible to support zeros in dates by disabling the strict mode, thus, silencing other types of errors.

Because NO_ZERO_IN_DATE is deprecated, it will be removed in a future MySQL release as a separate mode name and its effect included in the effects of strict SQL mode.

My requirement was to build a monthly view of a table. I had to add an index on month. So, computing moth on-the-fly with YEAR() and MONTH() was not an option.

Generated columns served their purpose. The year and month columns weren't part of the primary index, and I could even save space thanks to the VIRTUAL (not STORED) generated columns.

Links

• https://dev.mysql.com/doc/refman/5.7/en/sql-mode.html#sqlmode_no_zero_in_date
• https://dev.mysql.com/doc/refman/5.7/en/create-table-generated-columns.html

Answer 5

I would store the two as two separate columns as integers. It would make validation cake and allow quick and easy sorting and grouping possibilities.

Answer 6

It says in the MySQL manual that you can store partial dates

http://dev.mysql.com/doc/refman/5.1/en/date-and-time-functions.html#function_date-format

Ranges for the month and day specifiers begin with zero due to the fact that MySQL permits the storing of incomplete dates such as '2014-00-00'.

This means that to store the year and month only, you can use a DATE column and put 00 instead of the day. e.g 2013-12-00.

Related: Store incomplete date in MySQL date field