MySQL 8.0

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CREATE TABLE wppp_term_relationships (
  `object_id` INTEGER,
  `term_taxonomy_id` INTEGER
);

INSERT INTO wppp_term_relationships
  (`object_id`, `term_taxonomy_id`)
VALUES
  ('1234', '2010'),
  ('2344', '30453');

Records: 2  Duplicates: 0  Warnings: 0


CREATE TABLE wppp_terms (
  `term_id` INTEGER,
  `name` VARCHAR(6)
);

INSERT INTO wppp_terms
  (`term_id`, `name`)
VALUES
  ('30453', '2010'),
  ('2010', 'toy');

Records: 2  Duplicates: 0  Warnings: 0


UPDATE wppp_term_relationships tr
JOIN wppp_terms t ON tr.term_taxonomy_id =  t.term_id
SET tr.term_taxonomy_id = t.name 
WHERE t.name REGEXP '^[0-9]*$';

Rows matched: 1  Changed: 1  Warnings: 0


SELECT * FROM wppp_term_relationships;


object_id
term_taxonomy_id


1234
2010

2344
2010