How to get php value in another table for aydishnik?

There is a MySQL table with categories, each category with its id.
And there there's a table with additional descriptions, she has an item_id corresponding to aydishnik the first table.
For example:
Table #__category in her line of Concrete blocks with id=20
and the table #__category_description the line the Price of blocks with id=1, item_id=20 and value=1000
Here I need to get exactly a value of 1000 from the second table.
June 3rd 19 at 19:40
2 answers
June 3rd 19 at 19:42
Select d.value from category c 
 inner join description d
 on = d.item_id
June 3rd 19 at 19:44
I understand the second table - EAV,
then there should be something like this:
request wrote
where d.item_description = "Price blocks"

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