shell - Update query wrong in MySQL

Question

各位大侠， 请问哪错了？

Select * from rc where business_date = '2017-03-21 16:50:29.032'. IF
cutoff_dt` is null or empty, it will update, otherwise display not
null

  #!/bin/bash
    mysql -u root -pPassword <<rc
    use rc;
    SELECT *,
           CASE 
             WHEN cutoff_dt IS NULL
           THEN 
             UPDATE rc SET cutoff_dt = '2017-03-21 00:00:00.0'
             ELSE 'NOT NULL'
          END
    from rc
    WHERE business_date = '2017-03-21 16:50:29.032';
    rc

错误

ERROR 1064 (42000) at line 2: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'UPDATE rc SET cutoff_dt = '2017-03-21 00:00:00.0'
     ELSE ' at line 5

Answer 1

據我所知，then後面跟的應該是個result，不知道是不是這麼回事