一维表转2维表 2

   
    SELECT t_no , SUM(CASE WHEN w_no=1 THEN 1 END) AS 星期一,
SUM(CASE WHEN w_no=2 THEN 1 END) AS 星期二,
SUM(CASE WHEN w_no=3 THEN 1 END) AS 星期三
FROM teacher_class
GROUP BY t_no