mysql查询if语句case when then

在mysql中如何写if语句

```
select count(*), (CASE userid WHEN '131' THEN '张三' WHEN '132' THEN '李四' WHEN '133' THEN '王五' WHEN '134' THEN '赵六' ELSE '保密' END) as renming from log where status=1 group by renming;
```