Question

我有这样的SQL请求：

SELECT date_format(`user_date_accountcreated`, "%Y-%m-%d") as date, Count(*) as total from users 
where `user_date_accountcreated` 
BETWEEN '2016-09-18 00:00:00' AND '2016-10-03 23:59:59' 
GROUP BY date_format(`user_date_accountcreated`, "%y%m%d")

但是当没有记录时，由于GROUP BY我的结果是空的，没有什么可以分组......

我尝试使用ISNULL这样：

SELECT date_format(`user_date_accountcreated`, "%Y-%m-%d") as date, ISNULL(Count(*), 0) as total from users 
where `user_date_accountcreated` BETWEEN '2016-09-18 00:00:00' AND '2016-10-03 23:59:59'
GROUP BY date_format(`user_date_accountcreated`, "%y%m%d")

但我得到一个SQL错误：＃1582 - 调用本机函数时参数计数不正确＆＃39; ISNULL＆＃39;

当我们使用GROUP BY？

时，有机会获得0而不是空结果

Answer 1

使用条件聚合：

SELECT DATE_FORMAT(user_date_accountcreated, "%Y-%m-%d") AS date,
       SUM(CASE WHEN user_date_accountcreated BETWEEN '2016-09-18 00:00:00' AND
                                                  '2016-10-03 23:59:59'
            THEN 1 ELSE 0 END) AS total_from_users
GROUP BY DATE_FORMAT(user_date_accountcreated, "%y%m%d")

Answer 2

检查

SELECT
  date_format(`user_date_accountcreated`, "%Y-%m-%d") as date, 
  Count( date_format(`user_date_accountcreated`, "%Y-%m-%d") )  as total
from users 
where `user_date_accountcreated` 
BETWEEN '2016-09-18 00:00:00' AND '2016-10-03 23:59:59' 
GROUP BY date_format(`user_date_accountcreated`, "%y%m%d")

Answer 3

首先，查询无法返回不存在的记录。如果你想看到它们，你必须生成它们。以下查询使用UNION ALL在查询未返回任何行时从查询或生成的记录中获取记录：

[HTTP] --> POST /wd/hub/session/9d9d5814-2085-4f25-bb5e-e4cc0838fa25/elements {"using":"id","value":"Performances button"}
[MJSONWP] Calling AppiumDriver.findElements() with args: ["id","Performances button"...
[debug] [BaseDriver] Waiting up to 0 ms for condition
[debug] [AndroidBootstrap] Sending command to android: {"cmd":"action","action":"find","params":{"strategy":"id","selector":"Performances button","context":"","multiple":true}}
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got data from client: {"cmd":"action","action":"find","params":{"strategy":"id","selector":"Performances button","context":"","multiple":true}}
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got command of type ACTION
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got command action: find
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] Finding 'Performances button' using 'ID' with the contextId: '' multiple: true
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] Using: UiSelector[RESOURCE_ID=uk.co.bbc.music:id/Performances button]
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] getElements selector:UiSelector[RESOURCE_ID=uk.co.bbc.music:id/Performances button]
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] Element[] is null: (0)
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] getElements tmp selector:UiSelector[INSTANCE=0, RESOURCE_ID=uk.co.bbc.music:id/Performances button]
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] Using: UiSelector[RESOURCE_ID=android:id/Performances button]
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] getElements selector:UiSelector[RESOURCE_ID=android:id/Performances button]
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] Element[] is null: (0)
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] getElements tmp selector:UiSelector[INSTANCE=0, RESOURCE_ID=android:id/Performances button]
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] Using: UiSelector[DESCRIPTION=Performances button]
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] getElements selector:UiSelector[DESCRIPTION=Performances button]
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] Element[] is null: (0)
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] getElements tmp selector:UiSelector[DESCRIPTION=Performances button, INSTANCE=0]
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] Element[] is null: (1)
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] getElements tmp selector:UiSelector[DESCRIPTION=Performances button, INSTANCE=1]
[AndroidBootstrap] [BOOTSTRAP LOG] [debug] Returning result: {"status":0,"value":[{"ELEMENT":"11"}]}
[debug] [AndroidBootstrap] Received command result from bootstrap
[MJSONWP] Responding to client with driver.findElements() result: [{"ELEMENT":"11"}]
[HTTP] <-- POST /wd/hub/session/9d9d5814-2085-4f25-bb5e-e4cc0838fa25/elements 200 80730 ms - 90

使用with子句可以实现同样的目的：

SELECT 
  date_format(user_date_accountcreated, '%Y-%m-%d') AS date, 
  COUNT(*) AS total
FROM users 
WHERE user_date_accountcreated >= '2016-09-18' 
  AND user_date_accountcreated < '2016-10-04' 
GROUP BY date_format(user_date_accountcreated, '%Y-%m-%d')
UNION ALL
SELECT null, 0
WHERE NOT EXISTS
(
  SELECT *
  FROM users 
  WHERE user_date_accountcreated >= '2016-09-18' 
    AND user_date_accountcreated < '2016-10-04' 
);

我还纠正了你的查询中的两个错误：

SQL字符串分隔符为WITH mydates AS ( SELECT date_format(user_date_accountcreated, '%Y-%m-%d') AS date, COUNT(*) AS total FROM users WHERE user_date_accountcreated >= '2016-09-18' AND user_date_accountcreated < '2016-10-04' GROUP BY date_format(user_date_accountcreated, '%Y-%m-%d') ) SELECT date, total FROM mydates UNION ALL SELECT null, 0 WHERE NOT EXISTS (select * from mydates);，如'。
您的选择列表应包含与（'%Y-%m-%d'与'%Y-%m-%'）分组相同的值。它适用于您的情况，但在其他情况下可能会导致问题。

按计数（*）和0分组而不是空

3 个答案: