mysql 字段 column 逗號分隔 值 value 變成列

If the name column were a JSON array (like '["a","b","c"]'), then you could extract/unpack it with JSON_TABLE() (available since MySQL 8.0.4):

select t.id, j.name
from mytable t
join json_table(
  t.name,
  '$[*]' columns (name varchar(50) path '$')
) j;

Result:

| id  | name |
| --- | ---- |
| 1   | a    |
| 1   | b    |
| 1   | c    |
| 2   | b    |

View on DB Fiddle

If you store the values in a simple CSV format, then you would first need to convert it to JSON:

select t.id, j.name
from mytable t
join json_table(
  replace(json_array(t.name), ',', '","'),
  '$[*]' columns (name varchar(50) path '$')
) j

Result:

| id  | name |
| --- | ---- |
| 1   | a    |
| 1   | b    |
| 1   | c    |
| 2   | b    |

View on DB Fiddle