sql查询将year设置为列名

Question

通过编写以下查询

SELECT item_name, YEAR( DATE ) , SUM( item_sold_qty ) 
FROM item
JOIN sales ON item.id = sales.item_number
GROUP BY YEAR( DATE ) , item_name
ORDER BY item_name

我能够得到以下结果

item_name   YEAR( DATE )    SUM( item_sold_qty )
pencil          2011              22
pencil          2012              44
eraser          2012              22
eraser          2011              11
pen             2012              66
pen             2011              33
nib             2012              88
nib             2011              44

相反,我希望以下列方式得到结果

 item_name      2011    2012
    pencil       22      44            
    eraser       11      22                   
    pen          33      66                  
    nib          44      88

我不是很擅长sql,并且不知道如何将年份设置为列名.需要帮忙.

注意 ::我的数据库有2个表.销售表的日期列有不同的日期,如2012-03-01,2012-04-02,2011-07-03,等......

Answer 1

也许是这样的:

SELECT 
    item_name, 
    SUM(CASE WHEN YEAR( DATE )=2011 THEN item_sold_qty ELSE 0 END) AS '2011',
    SUM(CASE WHEN YEAR( DATE )=2012 THEN item_sold_qty ELSE 0 END) AS '2012'
FROM 
    item
JOIN sales ON item.id = sales.item_number
GROUP BY
    item_name
ORDER BY 
    item_name

编辑

如果你想要其他年份并仍然总结它们.然后你可以这样做:

SELECT 
    item_name, 
    SUM(CASE WHEN YEAR( DATE )=2011 THEN item_sold_qty ELSE 0 END) AS '2011',
    SUM(CASE WHEN YEAR( DATE )=2012 THEN item_sold_qty ELSE 0 END) AS '2012',
    SUM(CASE WHEN NOT YEAR( DATE ) IN (2011,2012) THEN item_sold_qty ELSE 0 END) AS 'AllOtherYears'
FROM 
    item
JOIN sales ON item.id = sales.item_number
GROUP BY
    item_name
ORDER BY 
    item_name

EDIT2

如果你有很多年,而且你不想继续增加岁月.然后你需要使用动态sql.这意味着您连接sql的varchar然后执行它.

有用的参考文献:

• MySQL数据透视表,包含基于单列数据的动态标头
• 如何在MySQL存储过程中使用动态SQL
• MySQL/Pivot表
• MYSQL - 行到列