Shulou(Shulou.com)06/01 Report--

Group by expression or function:

# case: grouped according to the length of employees' names, query the number of employees in each group, and select more than five employees

SELECT COUNT (*), LENGTH (last_name) FROM employeesGROUP BY LENGTH (last_name) HAVING COUNT (*) > 5

Group by multiple fields:

# case: query the average salary of employees for each type of work in each department

SELECT AVG (salary), department_id,job_idFROM employeesGROUP BY department_id,job_id

Sort

# case: query the average salary of employees whose department number is not null in each department > 10000, and show it according to the average salary.

SELECT AVG (salary), department_id,job_idFROM employeesWHERE department_id IS NOT NULLGROUP BY department_id,job_idHAVING AVG (salary) > 10000ORDER BY AVG (salary) DESC

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