FROM Department d

JOIN RankedSalaries rONr.departmentId=d.id

WHEREr.salary_rank<=3;

[1667. Fix Names in a Table](https://leetcode.com/problems/fix-names-in-a-table)

SELECT user_id, CONCAT(UPPER(LEFT(name,1)),LOWER(RIGHT(name, LENGTH(name)-1)))AS name

FROM Users

ORDER BY user_id

[1527. Patients With a Condition](https://leetcode.com/problems/patients-with-a-condition)

SELECT patient_id, patient_name, conditions

FROM patients

WHERE conditionsLIKE'% DIAB1%'

OR conditionsLIKE'DIAB1%'

[196. Delete Duplicate Emails](https://leetcode.com/problems/delete-duplicate-emails)

DELETE p

FROM Person p, Person q

WHEREp.id>q.id

ANDq.Email=p.Email

[176. Second Highest Salary](https://leetcode.com/problems/second-highest-salary)

(SELECT DISTINCT Salary

FROM Employee

ORDER BY SalaryDESC

LIMIT1 OFFSET1)

AS SecondHighestSalary

[1517. Find Users With Valid E-Mails](https://leetcode.com/problems/find-users-with-valid-e-mails)

FROM Users

WHERE mail REGEXP'^[A-Za-z][A-Za-z0-9_\.\-]*@leetcode\\.com$'