SELECT - GROUP BY- Transact-SQL

https://docs.microsoft.com/en-us/sql/t-sql/queries/select-group-by-transact-sql

• GROUP BY ROLLUP
• GROUP BY CUBE ( )
• GROUP BY GROUPING SETS ( )

GROUP BY (Transact-SQL)

https://technet.microsoft.com/en-us/library/ms177673(v=sql.110).aspx

WITH CUBE

http://chiencong.com/thong-ke-trong-sql-server-bang-pivot-table/

SQL (Structured Query Language)

declare @Department as table (DeptID INT IDENTITY(1,1) PRIMARY KEY,DeptName NVARCHAR(50))
declare @Employee as table (EmpID INT IDENTITY(1,1) PRIMARY KEY,DeptID INT, EmpName NVARCHAR(50),Salary bigint)

insert into @Department(DeptName) select 'Developer' union all select 'Accountant' union all select 'Tester'
insert into @Employee(DeptID,EmpName,Salary) select 1,'Manh',2000 union all select 1,'Chinh',1000 union all select 1,'Van',800 union all select 1,'Linh',1500 union all select 1,'Thu',1500 union all select 2,'Mai',500 union all select 2,'Vuong',1500 union all select 2,'Lien',1200 union all select 2,'Huong',800 union all select 2,'Phi',1500 union all select 3,'Dau',1500 union all select 3,'Chien',1200 union all select 3,'Cuong',800

--Chọn ra những department nào có ít nhất 3 employee salary > 1000
select d.DeptName from @Employee e join @Department d on e.DeptID = d.DeptID
where e.Salary > 1000 group by e.DeptID, d.DeptName having count(e.DeptID) >= 3