如何在按月分组日期时将一个月从INT转换为VARCHAR

Question

我需要以一种可读的方式总结这些年来每个月的面试次数。

SELECT month(i.Date) AS Month, Year(i.Date) AS Year, Count(i.Id) AS' Number of Interviews'
FROM Interviews i
GROUP BY month(i.Date), year(i.Date)
ORDER BY year(i.Date) DESC, month(Date) ASC

我希望查询以VARCHAR的形式返回月份，类似于‘一月’，而不是从‘月份’函数中返回默认的INT。

Answer 1

对于MySql，应该是：

SELECT 
  monthname(i.Date) AS Month, 
  Year(i.Date) AS Year, 
  Count(i.Id) AS `Number of Interviews`
FROM Interviews i
GROUP BY month(i.Date), monthname(i.Date), year(i.Date)
ORDER BY year(i.Date) DESC, month(i.Date) ASC

对于 Server

SELECT 
  datename(month, i.date) AS Month, 
  Year(i.Date) AS Year, 
  Count(i.Id) AS [Number of Interviews]
FROM Interviews i
GROUP BY month(i.Date), datename(month, i.date), year(i.Date)
ORDER BY year(i.Date) DESC, month(i.Date) ASC

Answer 2

一个适用于大多数DBMS的解决方案是一个CASE表达式。

SELECT CASE month(i.date)
         WHEN 1 THEN
           'January'
         ...
         WHEN 12 THEN
           'December'
       END month,
       year(i.date) year,
       count(i.id) number_of_interviews
       FROM interviews i
       GROUP BY month(i.date),
                year(i.date)
       ORDER BY year(i.date) DESC,
                month(i.date) ASC;

Answer 3

SELECT count(1), format(dateColumn, 'yyyy-MM')
FROM tableName
GROUP BY format(dateColumn, 'yyyy-MM')
ORDER BY 2