链接将表连接到导轨

Question

I'm trying to join multiple tables together and then make a query but I'm running into a syntax error.

I have the following tables:

achievement_standards
  id
  description

terms
  start_date
  end_date
  term_year_id

term_standards
  term_id
  achievement_standard_id

And I have the following method:

def school_standards
  @standards = @school.achievement_standards
  .joins("LEFT OUTER JOIN term_standards ON achievement_standards.id = term_standards.achievement_standard_id")
  .joins("LEFT OUTER JOIN terms ON terms.id = term_standards.term_id")
  .where("term_standards.id IS ? OR (term_standards.term_id IS NOT ? AND terms.term_year_id IS NOT ?)", nil, nil, 100),

end

I'm getting a syntax error at or near "100" . Is there something wrong with how I joined the tables? I'm trying to get achievement standards that are not in the term_standards table or ones that are not in the term_year 100.

Answer 1

The last part of your query :

... AND terms.term_year_id IS NOT ?

When given param 100 , this will expand as :

... AND terms.term_year_id IS NOT 100

This is not valid SQL : IS is not to compare a value with a number, for this you would need to use the (in)equality operator. You probably want :

... AND terms.term_year_id <> ?

---

More generally speaking : in most RDBMS, IS is only used in conjonction with NULL (either IS NULL , or IS NOT NULL ). So basically this type of parameterized expressions can only be used with a NULL parameter (that is, the RDBMS will raise an error if passed another value) :

term_standards.id IS ?
term_standards.term_id IS NOT ?

Depending on your purpose, either you don't need to use parameters (make the ? explicitly NULL in your query), or you might want to refactor your query.