This lecture is on complex query SQL server, topic covered are:
• OUTPUT Clause
• RANK(), ROW_NUMBER() and DENSE_RANK() Function
• Query Optimization and Use of execution plan.



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----Basic but important functions
--ROW_NUMBER()
--RANK()
--DENSE_RANK()
--NTILE()

--ROW_NUMBER() --Returns a sequential row number with in partition of result set
use Northwind;
SELECT ROW_NUMBER() over(order by productid) as [Row No.], ProductName from Products;

----Getting alternate rows
------Odd Row
select * from (SELECT ROW_NUMBER() over(order by productid) as [Row No.], ProductName from Products) p where p.[Row No.]%2=1;
------Even Row
select * from (SELECT ROW_NUMBER() over(order by productid) as [Row No.], ProductName from Products) p where p.[Row No.]%2=0;
------Row Between
select * from (SELECT ROW_NUMBER() over(order by productid) as [Row No.], ProductName from Products) p where p.[Row No.]
Between 5 and ... Read more »

Union is to select all records from two table but common record only once.

Select * from tbemp1
UNION
Select * from tbemp2


Inersect is to select common records from two tables.

Select * from tbemp1
INTERSECT
Select * from tbemp2

Except(Minus) is equivalent to oracle minus clause. Select records of table 1 which are not in table 2.

Select * from tbemp1
EXCEPT
Select * from tbemp2

Get duplicate records from table
Select ename from tbemp a where a.eno!=(select Max(eno) from tbemp b where a.ename=b.ename)

Here eno denotes to employee number and ename denotes to employee name.

Without Data
Select * INTO tbem1 from tbemp where 1=2

Why 1=2?
Because none of the record could satisfy this condition i.e. 1=2. So no data would be copied into newly created table.

With Data
Select * INTO tbemp2 from tbemp

With Condition
Select * INTO tbemp3 from tbemp where depcod=102

Here depcod denotes to department code.

Select Alternate Row SQL Server

Their are many approaches to get alternate record from SQL server database table. Here i have discussed 2 approaches
1. Complex Query
2. Using Views

Complex Query: SELECT * from (SELECT ROW_NUMBER() OVER(ORDER BY Employee_id) as RowNumber, * from employees) T where t.RowNumber%2=0

Using Views:
CREATE VIEW with_rownumber
as
SELECT ROW_NUMBER() OVER(ORDER BY Employee_id) as RowNumber,* from employees;

SELECT * from with_rownumber where RowNumber%2=0

The approach preferred here is using VIEW because:
1. Easy to understand.
2. In future if you need to perform any operation related to RowNumber then you don't need to create another complex query. You could use view having rownumber column in it.