长sql优化

src/main/resources/mapper/course/CourseDao.xml

@@ -8,46 +8,31 @@
     </update>
     <select id="selectCourse" resultType="Map">
         SELECT
-        c.classify_id as classifyId,
-        c.course_id as courseId,
-        c.course_label as courseLabel,
-        c.create_time createTime,
+        c.classify_id AS classifyId,
+        c.course_id AS courseId,
+        c.course_label AS courseLabel,
+        c.create_time AS createTime,
         c.details,
         c.img,
-        c.banner_img as bannerImg,
+        c.banner_img AS bannerImg,
         c.status,
-        c.is_delete as isDelete,
-        c.msg_type msgType,
-        c.msg_url as msgUrl,
-        c.pay_num as payNum,
+        c.is_delete AS isDelete,
+        c.msg_type AS msgType,
+        c.msg_url AS msgUrl,
+        c.pay_num AS payNum,
         c.price,
-        c.wholesale_price as wholesalePrice,
-        c.is_over as isOver,
+        c.wholesale_price AS wholesalePrice,
+        c.is_over AS isOver,
         c.title,
-        c.is_price as isPrice,
-        c.title_img as titleImg,
-        c.update_time as updateTime,
-        cc.classification_name as classificationName,
-        c.course_type as courseType,
-        c.banner_id as bannerId,
-        b.name as bannerName,
-        0 as viewCounts,
-        c.dy_img_id as dyImgId,
-        c.dy_course_id as dyCourseId,
-        c.wx_course_id as wxCourseId,
-        c.wx_show as wxShow,
-        c.dy_show as dyShow,
-        c.sort,
-        round(10000*rand(),0) as goodNum,
-        ifnull(d.courseDetailsCount,0) as courseDetailsCount,
-        null AS courseDetailsName,
-        null AS courseDetailsId,
-        round(10000*rand(),0) as weekGoodNum,
-        0 as isRecommend
+        c.is_price AS isPrice,
+        c.title_img AS titleImg,
+        c.update_time AS updateTime,
+        c.course_type AS courseType,
+        c.banner_id AS bannerId,
+        COALESCE(d.courseDetailsCount, 0) AS courseDetailsCount
+
         FROM
         course AS c
-        LEFT JOIN course_classification AS cc ON c.classify_id = cc.classification_id
-        LEFT JOIN banner AS b ON b.id = c.banner_id
         LEFT JOIN (
         SELECT
         course_id,
@@ -58,8 +43,8 @@
         course_id
         ) AS d ON d.course_id = c.course_id
         WHERE
-        1 = 1
-        AND c.is_delete = 0
+        c.is_delete = 0
+
         <if test='null != wxShow and wxShow==1'>
             and c.wx_show = #{wxShow}
         </if>