SQL语句中容易出错的Case..........When

select st.username,
       st.userid,
       case st.sex
         when ‘1‘ then
          ‘男‘
         when ‘2‘ then
          ‘女‘
         else
          ‘其他‘
       end sex
  from students st

select st.username,
       st.userid,
       case
         when st.sex = ‘1‘ then
          ‘男‘
         when st.sex = ‘2‘ then
          ‘女‘
         else
          ‘其他‘
       end sex
  from students st

select case
         when col_1 in (‘a‘, ‘b‘) then
          ‘第一类‘
         when col_1 in (‘a‘) then
          ‘第二类‘
         else
          ‘其他‘
       end divclass
  from dual