Question

I’m trying to run a UPDATE using REPLACE on my MySQL database.

I have a WordPress database table (wp_postmeta) containing four fields: post_id, meta_id, meta_key, meta_value.

I would like to REPLACE all instances of denticulata with heteropoda but only if that post (i.e. that row’s post_id) also has a row where the meta_key is genus and meta_value is Corydoras.

For instance,

post_id     meta_id     meta_key    meta_value
4           14          breeding    Some stuff here about breeding denticulata
2           15          breeding    Some stuff here about breeding denticulata
4           16          genus       Corydoras
2           17          genus       Apistogramma

Only the row with meta_id of 14 should actually be altered there, as the rows with post_id of 2 aren’t from the Corydoras genus.

Is this possible? I have no idea where to start.

Thanks in advance,

Answer 1

UPDATE 
    wp_postmeta AS upd
  JOIN
    wp_postmeta AS chk
      ON  chk.post_id = upd.post_id
SET
    upd.meta_value = REPLACE(upd.meta_value, 'denticulata', 'heteropoda')
WHERE
      chk.meta_key = 'genus'
  AND chk.meta_value = 'Corydoras'
  AND upd.meta_key = 'breeding' ;           -- not sure if you need this line

Beware that this will also update 'denticulatas' with 'heteropodas' (and any other words that include the string denticulata) and that REPLACE() is case-sensitive, so Denticulata will not be replaced.