mysql - Inner join update query not running -

error in mysql syntax .i have used 2 tables join them using inner join

update wp_postmeta  set  sku.meta_value=seo.`meta description`   sanitaryseo  seo  inner join wp_postmeta sku  on sku.meta_value = seo.`product code` sku.meta_key='_yoast_wpseo_metadesc'  

you should define table , join in top

update wp_postmeta sku inner join sanitaryseo seo on sku.meta_value = seo.`product code` set  sku.meta_value=seo.`meta description`   sku.meta_key='_yoast_wpseo_metadesc';  

and remember update clause don't use .. (the table or tables joined in update clause)