具有连接表的高级查询和来自GET参数的多个值

Question

First of all I'm going to explain what I want to happen in the end so if you can't help me you don't waste your time reading all of this :)

I'm creating an API in which it outputs possible illnesses that a user could have, based on the symptoms they submitted.

I want the user to input something, this goes into the url as "symptom=... like: .../nameofmyapi/data?symptoms=headache+dizzyness. I retrieve the data from the GET parameter, but I have absolutely no idea on how to output the name of the illness.

My database looks like this:

• illness

  • illnessId (int(11), AUTO_INCREMENT)
  • illnessName(varchar(255))

• symptom

  • symptomId (int(11), AUTO_INCREMENT)
  • symptomName (varchar(255))

• illness_symptom

  • illnessId (from the illness table)
  • symptomId (from the symptom table)

This database design makes sure you dont get multiple values in 1 row and don't have the same values BUT like I said, I don't know how to "search" or "filter" illnesses based on values from the other table. Let alone having multiple symptoms to check on... seems impossible!

I've got this query though, so I can retrieve everything when the user did not input anything:

"SELECT illness.illnessId, illness.illnessName, symptom.symptomName FROM illness_symptom
 JOIN illness
 ON illness.illnessId = illness_symptom.illnessId
 JOIN symptom
 ON symptom.symptomId = illness_symptom.symptomId";

Which gives me this: image

Like I said, I only want to output "Whiplash" when the url looks like this:/nameofmyapi/data?symptoms=dizzyness+headache

Help would be appreciated!

Answer 1

First off all: To only output 'Whiplash' is not going to work because your other illness is also connected to the symptom 'dizzyness'.

I've created a database with your structure (only renamed the fields to have more default convention. Would also look at your table names to pluralfy them) and came up with this query:

SELECT i.id, i.name
FROM illness_symptom AS ils
JOIN illness AS i ON i.id = ils.illness_id
JOIN symptom AS s ON s.id = ils.symptom_id
WHERE s.name IN ('dizzyness',  'headache')
GROUP BY i.name

The IN part searches through your table and filters out all the other results with different symptoms. You could convert the result from your GET query to a comma separated list used in the query.

The GROUP BY part makes sure you won't get any double results. Off course you need to make sure a result only exists in your DB once (no double records with different case like 'whiplaSh').

Hope this helps!