更高效的查询来获取特定身体部位的所有症状？

Question

是否有更短/更有效的查询来替换它？

SELECT s_name 
FROM symptom, bodypart_symptoms, bodypart 
WHERE bodypart_symptoms.bp_id = bodypart.bp_id 
AND bodypart.bp_name = '$bodypart' 
AND symptom.s_id = bodypart_symptoms.s_id

表格结构：

bodypart： bp_id，bp_name

bodypart_symptoms： bp_id，s_id

疾病： d_id，d_name

disease_symptoms： d_id，s_id

症状： s_id，s_name

Answer 1

SELECT s_name 
FROM bodypart_symptoms
LEFT JOIN bodypart 
ON bodypart_symptoms.bp_id = bodypart.bp_id 
  AND bodypart.bp_name = '$bodypart' 
LEFT JOIN symptom
ON symptom.s_id = bodypart_symptoms.s_id

Answer 2

您应该像这样使用INNER JOIN

SELECT s_name
FROM symptom
INNER JOIN bodypart_simptoms
ON symptom.s_id = bodypart_symptoms.s_id
INNER JOIN bodypart 
ON bodypart_symptoms.bp_id = bodypart.bp_id 
WHERE bodypart.bp_name = '$bodypart'