操作数应包含1列数据库错误

Question

Hi guys I know this has been answered on here in a number of threads, but I just can't figure out what the error is in my query. I get the error 'Operand should contain 1 column(s)'. Looks like a monster of a query I'm building here, and any help will be appreciated:

SELECT u.* FROM (
(SELECT fx_users.id, CONCAT_WS(' ', last_name, first_name) as matched_field, 'person' as type 
    FROM fx_users 
    LEFT JOIN fx_profiles ON fx_profiles.user_id = fx_users.id 
    WHERE (fx_profiles.first_name, fx_profiles.last_name, fx_profiles.research_area LIKE '%a%' 
    OR fx_profiles.bio LIKE '%a%' 
    OR fx_profiles.institution LIKE '%a%' 
    OR fx_profiles.faculty LIKE '%a%' 
    OR fx_profiles.faculty_position LIKE '%a%' 
    OR fx_profiles.department LIKE '%a%' 
    OR fx_profiles.website LIKE '%a%' 
    OR fx_profiles.country LIKE '%a%' 
    OR fx_profiles.city LIKE '%a%' 
    OR fx_profiles.address LIKE '%a%' 
    OR fx_profiles.zip_code LIKE '%a%' 
    OR fx_profiles.keywords LIKE '%a%' ) 
) 
UNION (SELECT fx_publications.publication_id, fx_publications.title as matched_field, 'publication' as type 
    FROM fx_publications 
    WHERE ( publications.authors LIKE '%a%' 
    OR publications.year LIKE '%a%' 
    OR publications.title LIKE '%a%' 
    OR publications.reference LIKE '%a%' ) 
) 
UNION (SELECT fx_projects.project_id, fx_projects.title as matched_field, 'project' as type 
    FROM fx_projects 
    WHERE ( projects.title LIKE '%a%' 
    OR projects.description LIKE '%a%' ) 
)
) AS u 
ORDER BY id DESC 
LIMIT 0, 20

Any help will be appreciated. PS: This is part of a code in my Codeigniter Model.

Answer 1

This line doesn't make sense:

WHERE (fx_profiles.first_name, fx_profiles.last_name, fx_profiles.research_area LIKE '%a%' 

You should change it to:

WHERE (fx_profiles.first_name LIKE '%a%' or
       fx_profiles.last_name  LIKE '%a%' or
       fx_profiles.research_area LIKE '%a%' 
        . . .