MySQL查询返回等于或大于特定日期的行，其中日期以年，月和日列分隔

Question

A MySQL table EMPLOYEE has columns (beginyear, beginmonth, beginday, empid) all of type int.

What's a correct query to return all rows that are equal to or greater than the date 2009/8/13? That's year, month, day.

A query such as this is incorrect because it wouldn't return rows that contained dates such as 2009/9/1 (filtered out by beginday >=13 in where clause below) or 2010/1/14.

SELECT *
FROM EMPLOYEE
where beginyear >= 2009
  and beginmonth >= 8
  and beginday >=13

Assume I can't make any changes to the schema and that I have to create some sort of query from JDBC to get the results.

Answer 1

The best I could do with your bad situation of three different fields:

select *, concat(beginyear, '-',beginmonth,'-',beingday) as full_date 
  FROM TABLE 
   WHERE CONCAT(beginyear, '-',beginmonth,'-',beingday) >= '2009-08-13'

MySql's notion of a datetime expression is sort of peculiar, you might want to wrap the concat with a date() function to normalize it.