Searching in a JSON encoded string stored in a MySQL table field

I have this website made on Wordpress and for each post I have some additional fields. The values from those fields are stored in "wp_postmeta" table in the field" "meta_value" as a JSON encoded string.

Now the problem is that I have to build a search page where the use开发者_JAVA技巧r can search using those aditional fields as search criteria.

How can I lookup in that JSON string for each criteria?

Try using this plugin: http://wordpress.org/extend/plugins/wp-custom-fields-search/

It sounds like you're using custom fields. This plugin searches those.