sql 如何按列显示12个月份

如果你要在SQL中按列显示12个月份，可以使用CASE语句和聚合函数来实现。

假设你有一个名为`sales`的表，其中包含了每个月份的销售数据。你可以使用以下SQL查询来按列显示12个月份：

SELECT
  SUM(CASE WHEN MONTH(sale_date) = 1 THEN sales_amount ELSE 0 END) AS January,
  SUM(CASE WHEN MONTH(sale_date) = 2 THEN sales_amount ELSE 0 END) AS February,
  SUM(CASE WHEN MONTH(sale_date) = 3 THEN sales_amount ELSE 0 END) AS March,
  SUM(CASE WHEN MONTH(sale_date) = 4 THEN sales_amount ELSE 0 END) AS April,
  SUM(CASE WHEN MONTH(sale_date) = 5 THEN sales_amount ELSE 0 END) AS May,
  SUM(CASE WHEN MONTH(sale_date) = 6 THEN sales_amount ELSE 0 END) AS June,
  SUM(CASE WHEN MONTH(sale_date) = 7 THEN sales_amount ELSE 0 END) AS July,
  SUM(CASE WHEN MONTH(sale_date) = 8 THEN sales_amount ELSE 0 END) AS August,
  SUM(CASE WHEN MONTH(sale_date) = 9 THEN sales_amount ELSE 0 END) AS September,
  SUM(CASE WHEN MONTH(sale_date) = 10 THEN sales_amount ELSE 0 END) AS October,
  SUM(CASE WHEN MONTH(sale_date) = 11 THEN sales_amount ELSE 0 END) AS November,
  SUM(CASE WHEN MONTH(sale_date) = 12 THEN sales_amount ELSE 0 END) AS December
FROM sales;

以上查询将返回一个结果集，其中每个月份对应一列，列名为相应的月份名称，每个月份的值为该月份的销售总额。你可以根据实际表和字段名进行调整。