----------------query aggregation function and group by -------------------------
SELECT Test1.Test, avg(Test1.Id) As avg, SUM(Test1.Id) As SUm, COUNT(Test1.Id) As Count FROM [Test1]
GROUP BY Test1.Test
HAVING count(Test1.Id)< 3
---- Query data from multiply data tables----use select in------------------------
select Test1.Id, Test1.Test from Test1 where Test1.Id in
(select Test2.Id from Test2 where Test2.Name in (select Test3.Name from Test3 where Test3.Description = 'D2'))
---- Query data from multiply data tables----use with------------------------
with ba as ( select Test1.Id As Aid, Test2.Id As BID, Test2.Name from Test1 inner join Test2 on Test1.Id = Test2.Id )
select
* from ba
---- Query data from multiply data tables----------------------------
select
* from (select Test.BID, Test3.Description from
(
select Test1.Id As Aid, Test2.Id As BID, Test2.Name from Test1 inner join Test2 on Test1.Id = Test2.Id where Test1.Id = 1) Test
inner join Test3 on Test.Name = Test3.Name ) Test3333
select Test1.Id As Aid, Test2.Id As BID, Test2.Name from Test1 inner join Test2 on Test1.Id = Test2.Id where Test1.Id = 1
select * from Test2
select * from Test3