SQL-是否可以替换uuid主键中的值？

Question

I have a test table having say ID field (primary key) with values like (abcd1234, mnop5678). Now I want to replace all values of ID to introduce hyphens so that the value becomes (abcd-1234, mnop-5678). How do I do it using SQL)?

PS: The real use case is that the ID field used to be an alphanumeric value and is now changed to uuid format (having multiple hyphens in 8-4-4-4-12 format) Ask is to convert the existing data so as to avoid doing a truncate and reload of data as it contains millions of rows. Sorry for any typos, typing using mobile.

Answer 1

MYSQL Solution:
Suppose we have a table test1 where primary key is of varchar type, refer below table structure.

CREATE TABLE `test1` (
 `id` varchar(20) NOT NULL COMMENT 'Primary Key',
 `name` varchar(255) DEFAULT NULL COMMENT 'Name',
 PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1  

Inserting sample records:

INSERT INTO `test1` (`id`, `name`) VALUES ('abcd1234', 'abcd');
INSERT INTO `test1` (`id`, `name`) VALUES ('mnop5678', 'mnop');

Now performing update query, where we are considering ID field format should be first 4 characters are letter, 5th character is -(hyphen) & then after numbers.

UPDATE `test1` SET `id` = CONCAT(SUBSTRING(`id`, 1, 4), '-', SUBSTRING(`id`, 5)) WHERE 1;

Have excluded where clause here, because need to do update operation on complete table.

Answer 2

A sketch using some pseudo SQL dialect, as you didn't tag your DBMS:

1. You should first create a new column in the table with an UUID type.

    ALTER TABLE t ADD (new_id uuid); 

2. Then fill it with GUID.

    UPDATE t SET new_id = new_uuid(); 

3. Then alter all tables that reference the table as well.

    ALTER u ADD (new_t uuid); ... 

4. Update them as well.

    UPDATE u SET new_t = (SELECT t.new_id FROM t WHERE t.id = ut); 

5. Drop the old column in the referencing tables.

    ALTER TABLE u DROP t; ... 

6. Drop the column in the table.

    ALTER TABLE t DROP id; 

7. Rename the column in the table.

    ALTER TABLE t RENAME new_id TO id; 

8. Rename the column in the referencing tables.

    ALTER TABLE u RENAME new_t TO t; ... 

9. Reintroduce the constraints on the table.

    ALTER TABLE t ADD (PRIMARY KEY (id)); 

10. Reintroduce the constraints on the referencing tables.

     ALTER TABLE u ADD (FOREIGN KEY (t) REFERENCES t (id)); 

You might also need to reindex the columns depending on the indexes you had on the old columns.