查询时遇到一些问题。我正在尝试从表中创建select,其中deposit_type_language_id = 3或者如果行不存在1(作为后备),并通过deposit_type_id进行分组。
+-----------------+--------------------------+-------------------+
| deposit_type_id | deposit_type_language_id | deposit_type_name |
+-----------------+--------------------------+-------------------+
| 1 | 1 | jewellery |
| 1 | 2 | bijuterii |
| 1 | 3 | šperky |
| 2 | 1 | equipment |
| 2 | 2 | tehnica |
+-----------------+--------------------------+-------------------+
我正在尝试以下查询:
SELECT t1.* from deposit_type AS t1
INNER JOIN
( SELECT deposit_type_id, min(deposit_type_language_id) from
deposit_type group by deposit_type_id ) AS t2
ON t1.deposit_type_id=t2.deposit_type_id group by deposit_type_id;
输出结果为:
+-----------------+--------------------------+-------------------+
| deposit_type_id | deposit_type_language_id | deposit_type_name |
+-----------------+--------------------------+-------------------+
| 1 | 1 | jewellery |
| 2 | 1 | equipment |
+-----------------+--------------------------+-------------------+
但我正在尝试实现以下内容:
+-----------------+--------------------------+-------------------+
| deposit_type_id | deposit_type_language_id | deposit_type_name |
+-----------------+--------------------------+-------------------+
| 1 | 3 | šperky |
| 2 | 1 | equipment |
+-----------------+--------------------------+-------------------+
我的错误在哪里?
表格结构:
deposit_type | CREATE TABLE `deposit_type` (
`deposit_type_id` smallint(5) unsigned NOT NULL,
`deposit_type_language_id` smallint(5) unsigned NOT NULL,
`deposit_type_name` varchar(96) NOT NULL,
PRIMARY KEY (`deposit_type_id`,`deposit_type_language_id`),
KEY `deposit_type_language_id` (`deposit_type_language_id`),
CONSTRAINT `deposit_type_ibfk_1` FOREIGN KEY (`deposit_type_language_id`) REFERENCES `language` (`language_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
答案 0 :(得分:1)
SELECT x.deposit_type_id
, COALESCE(y.deposit_type_language_id,x.deposit_type_language_id) deposit_type_language_id
, COALESCE(y.deposit_type_name,x.deposit_type_name) deposit_type_name
FROM deposit_type x
LEFT
JOIN deposit_type y
ON y.deposit_type_id = x.deposit_type_id
AND y.deposit_type_language_id = 3
WHERE x.deposit_type_language_id = 1;
答案 1 :(得分:0)
@CFreitas,我讨厌那个向你投票的男人。你回答错误一点但给了我一个想法。我们应该再添加一个比较,见下文。
SELECT t1.* from deposit_type AS t1
INNER JOIN
(SELECT deposit_type_id, max(deposit_type_language_id) as dtl FROM deposit_type
WHERE deposit_type_language_id=3 or deposit_type_language_id=1 group by deposit_type_id ) AS t2
ON t1.deposit_type_id=t2.deposit_type_id and t1.deposit_type_language_id=t2.dtl group by deposit_type_id;
输出结果为:
+-----------------+--------------------------+-------------------+
| deposit_type_id | deposit_type_language_id | deposit_type_name |
+-----------------+--------------------------+-------------------+
| 1 | 3 | šperky |
| 2 | 1 | equipment |
+-----------------+--------------------------+-------------------+