LeetCode 高频 SQL 50 题（基础版）之 【高级字符串函数 / 正则表达式 / 子句】· 上

题解：

select user_id, concat(upper(left(name,1)),lower(right(name,length(name)-1)))  name 
from Users
order by user_id

题解：

select * from Patients
where conditions regexp '^DIAB1|\\sDIAB1'

题解：

delete p1 
from Person p1,Person p2
where p1.email=p2.email and p1.id>p2.id

题解：

select ifNUll((select distinct salary 
from Employee
order by salary desc
limit 1,1),null) SecondHighestSalary