I’m struggling with SQL today. I’ve got a lookup table of a lookup table and can’t work out the SQL to do a search. As an example, consider the following:

Table 1 – books:

fields: book_id, price, title, author

example:

1, 2.99, ‘Life’, ‘A. Slug’

2, 4.99, ‘The Universe’, ‘A. Planet’

Table 2 – book_fields:

fields: field_id, field_name

example:

1, ‘cover_colour’

2, ‘cover_type’

Table 3 – book_field_lookup:

fields: book_id, field_id, field_value

1, 1, ‘blue’

1, 2, ‘hardback’

2, 1, ‘blue’

2, 2, ‘softback’

How do I find all hardback books that are blue?