我想知道為啥會產生兩條相同的班級

我執行下邊的sql語句

            SELECT 
                                    ti.id IndustryId,
                                    ti.ChineseName IndustryName,
                                    tcc.Id ClassId,
                                    tcc.Name ClassName,
                                    tcc.OriginalImgPath ClassImg,
                                    tcc.Price ClassPrice
                                FROM
                                    T_Course tc 
                                    LEFT JOIN T_CourseClass tcc ON tcc.Id = tc.ClassId
                                    LEFT JOIN T_CourseSubject tcs ON tcs.Id = tc.CourseSubjectId
                                    LEFT JOIN T_Category tca ON tcs.CategoryId=tca.Id 
                                    LEFT JOIN T_Industry ti ON tca.IndustryId=ti.Id 
                                    LEFT JOIN M_TrainingInstitutionIndustry mtii ON ti.Id=mtii.IndustryId 
                                WHERE
                                    tcc.IsDel=0  AND tcc.IsUsed=1 AND tcc.TrainingInstitutionId= mtii.TrainingInstitutionId
                                    AND tca.isDel=0
                                    AND ti.IsDel=0 AND ti.IsUsed=1
                                    AND mtii.IsDel=0 AND mtii.IsUsed=1
                                    AND mtii.TrainingInstitutionId=1
                                ORDER BY tcc.CreateTime DESC

得到下麵結果

誰能告訴我那一步沒有去重嗎？