查询MySQL数据库

Question

有人可以帮助我在此查询中添加包含疾病风险因素的第三个表。该表是tblRiskFactors

SELECT tblDiseases.disease 
FROM tblRel 
    LEFT JOIN tblDiseases ON tblRel.diseaseID = tblDiseases.diseaseID 
WHERE tblRel.symptomID = '1' AND tblRel.symptomID = '2' AND tblRel.symptomID ='3' 

Answer 1

SELECT tblDiseases.disease 
FROM tblRel 
     LEFT JOIN tblDiseases 
      ON tblRel.diseaseID = tblDiseases.diseaseID 
     LEFT JOIN tblRiskFactors 
      ON -- define the linking condition here 
WHERE tblRel.symptomID = '1' AND 
     tblRel.symptomID = '2' AND 
     tblRel.symptomID = '3' 

为了进一步获得更多的知识有关联接，请访问以下链接：

• Visual Representation of SQL Joins

Answer 2

SELECT tblDiseases.disease as disease 
FROM tblRel 
    LEFT JOIN tblDiseases ON tblRel.diseaseID = tblDiseases.diseaseID 
    LEFT JOIN tblRiskFactors ON tblRel.relation_column = tblRiskFactors.relation_column 
WHERE tblRel.symptomID in (1,2,3)