Concat（名字，“”，姓氏）就像OR电子邮件一样导致重复输出

I have an SQL query:

SELECT *
FROM user, user_company, company
WHERE user.user_id = user_company.user_id AND
      user_company.company_id = '$company_id' AND
      user_company.company_id = company.company_id AND 
      CONCAT(user.user_first_name, ' ', user.user_last_name) LIKE '%$l%' OR user.user_email LIKE '%$l%'
LIMIT 5

This seems to work on returning the values whether the user inputs something that's similar to the name or the email, however a flaw in this is if the user inputs the email, the record will be duplicated.

user_company doesn't contain any email data; it's only contained in the user table.

How do I stop that from happening?

Never use commas in the FROM clause. Always use proper, explicit, standard JOIN syntax.

Your problem is lack of parentheses. Try:

SELECT *
FROM user u JOIN
     user_company uc
     ON (user_id) JOIN
     company c
     ON (company_id)
WHERE uc.company_id = '$company_id' AND
      (CONCAT(u.user_first_name, ' ', u.user_last_name) LIKE '%$l%' OR
       u.user_email LIKE '%$l%'
      )
LIMIT 5