Question

I have a table in MySQL 4.0 which currently has a year field as a smallint(6) type. What will happen if I convert it directly to a Year type with a query like the following:

ALTER TABLE t MODIFY y YEAR(4) NOT NULL DEFAULT CURRENT_TIMESTAMP;

When the current members of column y have values like 2010? I assume that because the year type is technically values from 1-255, values above that will be truncated or broken.

So if MySQL isn’t smart enough to realize that 2010(int) = 110(year), what would be the simplest query or queries to convert the values?

Thanks for your help!

Answer 1

From MySQL Docs: 10.3.3 The year type

For four-digit format, MySQL displays YEAR values in YYYY format, with a range of 1901 to 2155, or 0000. For two-digit format, MySQL displays only the last two (least significant) digits; for example, 70 (1970 or 2070) or 69 (2069).

For years out of that range:

Illegal YEAR values are converted to 0000.

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A quick test

alter table foo add b year(4) not null default current_timestamp;
update foo set b=a;

a       b
1900    0000
1901    1901
1950    1950
2000    2000
2002    2002
2121    2121
2155    2155
2156    0000