Select in MySQL based on two tables
I have two tables.
diseases
-----------------------------
开发者_如何学编程| ID | NAME |
-----------------------------
| 1 | Disease 1 |
| 2 | Disease 2 |
| 3 | Disease 3 |
diseases_symptoms
-----------------------------
| DISEASE_ID | SYMPTOM_ID |
-----------------------------
| 1 | 1 |
| 1 | 2 |
| 1 | 3 |
| 1 | 4 |
| 2 | 1 |
| 2 | 2 |
I want to select all diseses which have symptoms 1 or 2 and 3 or 4.
I've tried:
SELECT *
FROM diseases_symtoms
WHERE (symptoms = '1' OR symptoms = '2')
AND (symptoms = '3' OR symptoms = '4')
And:
SELECT *
FROM diseases_symtoms
WHERE symptoms IN ('1','2')
AND symptoms IN ('3','4')
...but it is not working.
Keep in mind that SELECT can only examine one row at a time. Both those queries act as if you can detect a 1
and a 3
simultaneously (for example), which is not possible.
To consider multiple rows at once, you can either join to two separate copies of the table, or try a grouping like this:
SELECT diseases.*
FROM diseases
INNER JOIN diseases_symptoms ON (disases_symptoms.disease_id = diseases.disease_id)
GROUP BY diseases.disease_id
HAVING SUM(IF(symptoms = 1 OR symptoms = 2, 1, 0) > 0 AND SUM(IF(symptoms = 3 OR symptoms = 4, 1, 0) > 0
You could try...
SELECT DISTINCT *
FROM diseases
WHERE EXISTS (SELECT *
FROM disease_symptoms
WHERE disease.disease_id = disease_symptoms.disease_id AND
symptom_id IN (1,2)) AND
EXISTS (SELECT *
FROM disease_symptoms
WHERE disease.disease_id = disease_symptoms.disease_id AND
symptom_id IN (3,4));
SELECT d.* FROM diseases AS d
INNER JOIN disease_symptoms AS s1 ON s1.DISEASE_ID = d.ID WHERE SYMPTOM_ID IN (1, 2)
INNER JOIN disease_symptoms AS s2 ON s2.DISEASE_ID = d.ID WHERE SYMPTOM_ID IN (3, 4)
GROUP BY d.ID
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