Question

如果我有一个像这样的表my_table：

| id | val1 | val2|
| 1  | foo1 | bar |
| 2  | foo2 | baz |
| 3  | foo3 | bam |

我有一个硬编码的逗号分隔值列表，这些值是我通过编程生成的：spam, eggs, ham。

我想将我的值插入列val1中。我在想像这样的东西：

UPDATE my_table SET val1 = SELECT * FROM (VALUES ('spam'),('eggs'),('ham'))

但这给了我一个语法错误（MySQL 5.6.44）

最终结果应如下所示：

| id | val1 | val2|
| 1  | spam | bar |
| 2  | eggs | baz |
| 3  | ham  | bam |

Answer 1

DROP TABLE IF EXISTS my_table;

CREATE TABLE my_table
(id SERIAL PRIMARY KEY
,val1 VARCHAR(12) NOT NULL
,val2 VARCHAR(12) NOT NULL
);

INSERT INTO my_table VALUES
(1,'foo1','bar'),
(2,'foo2','baz'),
(3,'foo3','bam');

UPDATE my_table SET val1 = SUBSTRING_INDEX(SUBSTRING_INDEX('spam,eggs,ham',',',id),',',-1);

SELECT * FROM my_table;
+----+------+------+
| id | val1 | val2 |
+----+------+------+
|  1 | spam | bar  |
|  2 | eggs | baz  |
|  3 | ham  | bam  |
+----+------+------+

Answer 2

@Strawberry 的answer确实是模范。但是如果id的值不连续怎么办。

例如，id的值为2, 5, 6。在这种情况下，我们可以使用MariaDB 10.2 + / MySQL 8+中的Row_Number()功能来模拟连续的new_id。我还注意到，您输入的逗号分隔字符串在逗号后有空格。要处理此问题（可变的间距），我们可以在子字符串操作之后使用Trim()函数。以excellent answer by @Strawberry为基础：

模式（MySQL v8.0）-View on DB Fiddle

CREATE TABLE your_table_name
(id INT UNSIGNED PRIMARY KEY
,val1 VARCHAR(12) NOT NULL
,val2 VARCHAR(12) NOT NULL
);

INSERT INTO your_table_name VALUES
(2,'foo1','bar'),
(5,'foo2','baz'),
(6,'foo3','bam');

更新查询

UPDATE your_table_name t1
       JOIN (SELECT Row_number()
                      OVER (
                        ORDER BY id) AS new_id,
                    id
             FROM   your_table_name) t2
         ON t2.id = t1.id
SET    val1 =
Trim(Substring_index(Substring_index('spam, eggs,  ham', ',', t2.new_id), ',', -1));

检查数据

SELECT * FROM your_table_name;

| id  | val1 | val2 |
| --- | ---- | ---- |
| 2   | spam | bar  |
| 5   | eggs | baz  |
| 6   | ham  | bam  |

---

在旧版本的MySQL / MariaDB中，窗口功能不可用。在这种情况下，我们可以利用user-defined variables来模拟new_id：

模式（MySQL v5.7）-View on DB Fiddle

CREATE TABLE your_table_name
(id INT UNSIGNED PRIMARY KEY
,val1 VARCHAR(12) NOT NULL
,val2 VARCHAR(12) NOT NULL
);

INSERT INTO your_table_name VALUES
(2,'foo1','bar'),
(5,'foo2','baz'),
(6,'foo3','bam');

更新查询

UPDATE your_table_name t1
       JOIN (SELECT @rn := @rn + 1 AS new_id, 
                    id 
             FROM   your_table_name 
             CROSS JOIN (SELECT @rn := 0) vars
             ORDER BY id) t2
         ON t2.id = t1.id
SET    val1 =
Trim(Substring_index(Substring_index('spam, eggs,  ham', ',', t2.new_id), ',', -1));

检查数据

SELECT * FROM your_table_name;

| id  | val1 | val2 |
| --- | ---- | ---- |
| 2   | spam | bar  |
| 5   | eggs | baz  |
| 6   | ham  | bam  |

UPDATE SET列，每行具有不同的值

2 个答案:

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