MySQL COUNT 未提供正确的结果

Question

我正在尝试创建一个考勤应用程序，但我遇到了 SQL 语句问题。我需要它来计算有多少人出现和有多少人缺席，并获得每个辖区的总数。这是我设法想出的:

选择 IFNULL(precinct, 'Totals') 作为区域，COUNT(at.member_id) 作为 delegates_present，COUNT(ab.member_id) 作为 delegates_absent，COUNT(at.member_id) + COUNT(ab.member_id) as 'total' FROM 参加 LEFT JOIN 成员 m ON at.member_id = m.id LEFT JOIN 缺勤 ab ON ab.member_id = m.id GROUP BY precinct WITH ROLLUP

但显然，缺席列没有获取任何数据，它应该在 10-00 行中有一个 1。我做错了什么？我似乎无法弄清楚。

数据集、查询、结果和 fiddle :

DROP TABLE IF EXISTS absence;

CREATE TABLE `absence` (
  `id` int(11) NOT NULL,
  `member_id` varchar(255) NOT NULL,
  `member_email` varchar(255) NOT NULL,
  `member_phone` varchar(12) NOT NULL,
  `absent` tinyint(4) NOT NULL,
  `absence_desc` text NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO `absence` (`id`, `member_id`, `member_email`, `member_phone`, `absent`, `absence_desc`) VALUES
(1, '36227 ', '', '', 1, 'Out of town with family');

DROP TABLE IF EXISTS attendance;

CREATE TABLE `attendance` (
  `id` int(11) NOT NULL,
  `member_id` varchar(255) NOT NULL,
  `member_email` varchar(255) DEFAULT NULL,
  `member_phone` varchar(12) DEFAULT NULL,
  `present` tinyint(4) NOT NULL,
  `alternate` tinyint(4) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO `attendance` (`id`, `member_id`, `member_email`, `member_phone`, `present`, `alternate`) VALUES
(1, '11698 ', '<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="294344505b5d454c694a485a4a465a404e475a074a4644" rel="noreferrer noopener nofollow">[email protected]</a>', '704-788-9055', 1, NULL),
(2, '17698 ', '<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="5d2d3c2f342e356f6e1d243c353232733e3230" rel="noreferrer noopener nofollow">[email protected]</a>', '704-425-8868', 1, 1),
(3, '36228 ', '<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="cba0a8b9bebfa8a38ba8aab8a8a4b8a2aca5b8e5a8a4a6" rel="noreferrer noopener nofollow">[email protected]</a>', '704-309-5076', 1, 1),
(4, '16921 ', '<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="c1a0a5a2b3b4b5a2a981a2a0b2a2aeb2a8a6afb2efa2aeac" rel="noreferrer noopener nofollow">[email protected]</a>', '704-791-2685', 1, NULL),
(5, '1437 ', '<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="a1ccd6c2d3d4d5c2c9e1c2c0d2c2ced2c8c6cfd28fc2cecc" rel="noreferrer noopener nofollow">[email protected]</a>', '704-791-7373', 1, 1),
(6, '16922 ', '<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="452726373031262d05262436262a362c222b366b262a28" rel="noreferrer noopener nofollow">[email protected]</a>', '123-456-7890', 1, NULL);

DROP TABLE IF EXISTS members;

CREATE TABLE `members` (
  `id` int(11) NOT NULL,
  `last_name` varchar(20) DEFAULT NULL,
  `first_name` varchar(11) DEFAULT NULL,
  `middle_name` varchar(17) DEFAULT NULL,
  `suffix` varchar(3) DEFAULT NULL,
  `residential_address` varchar(48) DEFAULT NULL,
  `mailing_address` varchar(64) DEFAULT NULL,
  `precinct` varchar(5) DEFAULT NULL,
  `age` int(11) DEFAULT NULL,
  `ethnicity` varchar(2) DEFAULT NULL,
  `gender` varchar(1) DEFAULT NULL,
  `party` varchar(3) DEFAULT NULL,
  `race` varchar(1) DEFAULT NULL,
  `phone` varchar(12) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO `members` (`id`, `last_name`, `first_name`, `middle_name`, `suffix`, `precinct`) VALUES
    (1437, 'CRUTCHFIELD', 'MATTHEW', 'WILLIAM', NULL, '01-04'),
    (11698, 'MYRTLE', 'JEREMY', 'ALLEN', NULL, '02-03'),
    (16921, 'CRUTCHFIELD', 'ANDREW', 'DAVID', NULL, '02-08'),
    (16922, 'CRUTCHFIELD', 'BRITTANY', 'RENEE', NULL, '02-08'),
    (17698, 'MOFFITT', 'PARISH', 'HENRY', NULL, '02-08'),
    (36227, 'CRUTCHFIELD', 'CHERYL', 'JERMYN', NULL, '10-00'),
    (36228, 'CRUTCHFIELD', 'KEVIN', 'ROGER', NULL, '10-00');

SELECT IFNULL(precinct, 'Totals') as precinct, 
COUNT(at.member_id) as delegates_present, 
COUNT(ab.member_id) as delegates_absent, 
COUNT(at.member_id) + COUNT(ab.member_id) as 'total' 
FROM attendance at 
LEFT JOIN members m ON at.member_id = m.id 
LEFT JOIN absence ab ON ab.member_id = m.id 
GROUP BY precinct WITH ROLLUP;

+----------+-------------------+------------------+-------+
| precinct | delegates_present | delegates_absent | total |
+----------+-------------------+------------------+-------+
| 01-04    |                 1 |                0 |     1 |
| 02-03    |                 1 |                0 |     1 |
| 02-08    |                 3 |                0 |     3 |
| 10-00    |                 1 |                0 |     1 |
| Totals   |                 6 |                0 |     6 |
+----------+-------------------+------------------+-------+
5 rows in set, 1 warning (0.08 sec)

SHOW WARNINGS;
+---------+------+---------------------------------------------------+
| Level   | Code | Message                                           |
+---------+------+---------------------------------------------------+
| Warning | 1052 | Column 'precinct' in group statement is ambiguous |
+---------+------+---------------------------------------------------+

http://sqlfiddle.com/#!9/dc7e07/2/0

Answer 1

我认为您的加入顺序错误:

FROM members m
LEFT JOIN attendance at ON at.member_id = m.id 
LEFT JOIN absence ab ON ab.member_id = m.id

这应该有效。通过开始加入出勤表，您无需阅读完整的成员表。

让我知道它是否有效。