SELECT a.*,QC.CategoryName,QC.CategoryId,QOC.CategoryName as OblCategoryName,QOC.CategoryId as OblCategoryId,COALESCE(stats.cstat, 0) as cstat,COALESCE(stats.cuser, 0) as cuser,COALESCE(stats.place1, 0) as place1,COALESCE(stats.place2, 0) as place2,COALESCE(stats.place3, 0) as place3,COALESCE(stats.place4, 0) as place4
FROM dzp2r_ariquiz as a
LEFT JOIN dzp2r_ariquizquizcategory QQC ON a.QuizId = QQC.QuizId
LEFT JOIN dzp2r_ariquizcategory QC ON QQC.CategoryId = QC.CategoryId
LEFT JOIN dzp2r_ariquizquizoblcategory QQOC ON a.QuizId = QQOC.QuizId
LEFT JOIN dzp2r_ariquizoblcategory QOC ON QQOC.CategoryId = QOC.CategoryId
LEFT JOIN (
    SELECT 
        quiz_id,
        COUNT(id) as cstat,
        SUM(state_user) as cuser,
        SUM(CASE WHEN place_name = "1" THEN 1 ELSE 0 END) as place1,
        SUM(CASE WHEN place_name = "2" THEN 1 ELSE 0 END) as place2,
        SUM(CASE WHEN place_name = "3" THEN 1 ELSE 0 END) as place3,
        SUM(CASE WHEN place_type = "Лауреат" THEN 1 ELSE 0 END) as place4
    FROM dzp2r_testres_diplom
    WHERE quiz_id = 3622
    GROUP BY quiz_id
) as stats ON stats.quiz_id = a.QuizId
WHERE a.Status = 1 AND a.QuizId = 3622

Муха-Цокотуха (Корней Чуковский)

Принять участие