MySQL通過group_concat退出連接

Question

我在創建表和查詢時遇到了SQL Fiddle： http ://www.sqlfiddle.com/#!9/3404e /1

這是表創建腳本：

CREATE TABLE IF NOT EXISTS `collection` (
  `id` bigint(20) unsigned NOT NULL,
  `name` varchar(50) NOT NULL,
  `label` varchar(120) NOT NULL,
  `label_plural` varchar(120) NOT NULL);

INSERT INTO `collection` (`id`, `name`, `label`, `label_plural`) VALUES
    (1, 'account', 'Account', 'Accounts');

CREATE TABLE IF NOT EXISTS `field` (
  `id` bigint(20) unsigned NOT NULL,
  `name` varchar(50) NOT NULL,
  `label` varchar(120) NOT NULL,
  `collection_id` bigint(20) unsigned NOT NULL);

INSERT INTO `field` (`id`, `name`, `label`, `collection_id`) VALUES
    (1, 'name', 'Name', 1),
    (2, 'state', 'State', 1);

CREATE TABLE IF NOT EXISTS `option` (
  `id` bigint(20) unsigned NOT NULL,
  `record_type_id` bigint(20) unsigned DEFAULT NULL,
  `field_id` bigint(20) unsigned NOT NULL,
  `value` varchar(120) NOT NULL);

INSERT INTO `option` (`id`, `record_type_id`, `field_id`, `value`) VALUES
    (1, NULL, 2, 'CO'),
    (2, NULL, 2, 'NE'),
    (3, NULL, 2, 'BC'),
    (4, NULL, 2, 'MB'),
    (5, 1, 2, 'CO'),
    (6, 1, 2, 'NE'),
    (7, 2, 2, 'BC'),
    (8, 2, 2, 'MB');

CREATE TABLE IF NOT EXISTS `record_type` (
  `id` bigint(20) unsigned NOT NULL,
  `name` varchar(120) NOT NULL,
  `collection_id` bigint(20) unsigned NOT NULL);

INSERT INTO `record_type` (`id`, `name`, `collection_id`) VALUES
    (1, 'US', 1),
    (2, 'Canada', 1);

這是我要運行的查詢：

select
    `field`.`name`,
    `field`.`label`,
    ifnull(group_concat(`option`.`value` separator ';'), '') as `options`
from
    `field`
join
    `collection` on
        `collection`.`id` = `field`.`collection_id`
join
    `record_type` on
        `record_type`.`collection_id` = `collection`.`id`
left join
    `option` on
        `option`.`record_type_id` = `record_type`.`id` and
        `option`.`field_id` = `field`.`id`
where
    `record_type`.`name` = 'US' and
    `collection`.`name` = 'account';

我期望的是兩行，如下所示：

+-------+-------+---------+
| name  | label | options |
+-------+-------+---------+
| name  | Name  | NULL    |
| state | State | CO;NE   |
+-------+-------+---------+

但是我只收到狀態行。 如果刪除group_concat行，則會得到如下三行，因此我知道一切都將返回：

+-------+-------+--------+
| name  | label | option |
+-------+-------+--------+
| name  | Name  | NULL   |
| state | State | CO     |
| state | State | NE     |
+-------+-------+--------+

Answer 1

基本上，您缺少GROUP BY ， GROUP_CONCAT()將組中的所有值連接在一起，沒有GROUP BY的話，只有一個組。

嘗試這個;

select
    `field`.`name`, `field`.`label`,
    group_concat(`option`.`value` separator ';') as `options`
from `field`
join `collection` 
  on `collection`.`id` = `field`.`collection_id`
join `record_type` 
  on `record_type`.`collection_id` = `collection`.`id`
left join `option` 
  on `option`.`record_type_id` = `record_type`.`id` 
 and `option`.`field_id` = `field`.`id`
where `record_type`.`name` = 'US' 
  and `collection`.`name` = 'account'
GROUP BY `field`.`name`,`field`.`label`

帶有更正的SQLfiddle 。

Answer 2

查詢的主要問題是您沒有group by子句。

此外，您where的條件是“撤銷”的left join S，把它們變成inner join秒。 下面完成了您想要的：

select
    `field`.`name`,
    `field`.`label`,
    ifnull(group_concat(`option`.`value` separator ';'), '') as `options`
from
    `field`
join
    `collection` on
        `collection`.`id` = `field`.`collection_id` and
        `collection`.`name` = 'account'
join
    `record_type` on
        `record_type`.`collection_id` = `collection`.`id` and
        `record_type`.`name` = 'US' 
left join
    `option` on
        `option`.`record_type_id` = `record_type`.`id` and
        `option`.`field_id` = `field`.`id`
group by field.name, field.label;