11.18 学习

1.sql

select m.user_id,round(ifnull(cfnum/p,0),2) confimation_rate from 
    (select a.user_id,ifnull(num,0) p from Signups a 
        left join (select user_id,count(*) num from Confirmations 
        group by user_id)b 
        on a.user_id=b.user_id) m left join
    (select user_id,count(*)cfnum from Confirmations 
    where action='confirmed' 
    group by user_id) n
        on m.user_id=n.user_id;

2.try catch

    @Override
    public R<ModelCenterVO> fetchByModelCode(String modelCode) {
        try {
            result=
            	...
                .one();
            return R.ok(result);
        } catch (TooManyResultsException e) {
            log.error(
                    "查询到多个结果,错误类型={},错误信息={}",
                    e.getClass().getName(),
                    e.getMessage());
            return R.fail("modelCode查询到多个模型");
        } catch (Exception e) {
            log.error(
                    "内部错误,错误类型={},错误信息={}",
                    e.getClass().getName(),
                    e.getMessage());
            return R.fail("内部错误");
        }
    }