MySQL如何将多个查询合并为一个查询

Question

假设我有一个名为“productClick”的表，如下所示：

----id------click-------------ctime----------
|    1  |    5     |   2015-12-26 00:01:12  |
---------------------------------------------
|    2  |    2     |   2015-12-27 00:01:12  |
---------------------------------------------
|    3  |    7     |   2015-12-28 00:01:12  |
---------------------------------------------
|    4  |    1     |   2015-12-28 00:01:12  |
---------------------------------------------

我想获取产品总数、今天添加的产品总数和总点击次数。

我有三个这样的独立查询：

SELECT COUNT(*) as totalProduct FROM productClick
SELECT COUNT(*) as todayTotalProductAdded FROM productClick WHERE DATE(`ctime`) = CURDATE()
SELECT sum(click) as totalClick FROM productClick

它工作正常。但我想将这三个单独的查询组合成一个查询。如何做到这一点？

更新

问题已更新。对不起我的错。谢谢@Gordon Linoff

Answer 1

您可以使用条件聚合：

SELECT COUNT(*) as totalProduct,
       SUM(click) as totalClick,
       SUM(DATE(ctime) = CURDATE()) as todayClick
FROM productClick

todayClick 是以下的简写：

SUM(CASE WHEN DATE(ctime) = CURDATE() THEN 1 ELSE 0 END) as todayClick

或者UNION ALL如果你想要多行：

SELECT 'totalProduct' AS counter_name, COUNT(*) AS counter_value FROM productClick
UNION ALL
SELECT 'todayClick', COUNT(*) FROM productClick WHERE DATE(ctime) = CURDATE()
UNION ALL 
SELECT 'totalClick', SUM(click) FROM productClick

编辑：

今天添加的产品总数和总点击次数。

SELECT COUNT(*) as totalProduct,
       SUM(click) as totalClick,
       SUM(CASE WHEN DATE(ctime) = CURDATE() THEN click ELSE 0 END) as todayClick
FROM productClick