Your UPDATE command would look like so after all variables are substituted — and in this example, the table prefix is wp_ (the default one), $group['1C_id'] is 9095b4cf-969d-11e9-a601-5cf3706390c8, and $found_id (the term ID) is 123.
UPDATE `wp_termmeta`
SET `meta_key` = '1C_id', `meta_value` = '9095b4cf-969d-11e9-a601-5cf3706390c8'
WHERE `term_id` = 123
So that means, all existing meta where the term ID is 123 and regardless what the meta key is, will be changed:
First, the meta key is set to 1C_id, so the tax_position meta was renamed to 1C_id.
Secondly, the meta value is set to 9095b4cf-969d-11e9-a601-5cf3706390c8, which became the tax_position's new value.
So that explains this: "This deletes the tax_position meta and duplicates the 1C_id meta row".
I.e. The tax_position meta was not deleted, but only its key and value that were changed, and that they're set to the same ones for the existing 1C_id meta.
Therefore, $wpdb->update() did not actually delete or add any metadata. It's your query which isn't done correctly.
So maybe you're trying to do something like this?
Note that I used $wpdb->prepare() to prepare the query for safe execution, and you should do the same.
// Select meta IDs by meta value.
$meta_ids = $wpdb->get_col( $wpdb->prepare( "
SELECT meta_id FROM $wpdb->termmeta
WHERE meta_value = %s
", $group['1C_id'] ) );
// Then update all the above meta by the meta ID.
if ( ! empty( $meta_ids ) ) {
$wpdb->query( $wpdb->prepare( "
UPDATE $wpdb->termmeta
SET meta_key = '1C_id', meta_value = %s
WHERE meta_id IN (" . implode( ',', $meta_ids ) . ")
", $group['1C_id'] ) );
/* Or you can use update_metadata_by_mid():
foreach ( $meta_ids as $meta_id ) {
update_metadata_by_mid( 'term', $meta_id, $group['1C_id'], '1C_id' );
}
*/
}
But then, why are you UPDATE-ing the meta value with the same value ($group['1C_id']) used when SELECT-ing the meta? Was that a typo? (Maybe you just wanted to update the meta key..?)
