Significance of ORDER BY <particular multiple number> - mysql

Question

Help me understand the following snippet:
...
ORDER BY 2, 12, 11

Answer 1

In SQL ORDER BY is the Keyword used to Order your Resultset based on the values of a Particular column or Columns either Ascending or Descending order.
The ORDER BY is Given as the Last Statement in a SELECT.
The Syntax is :
SELECT
<List of Columns>
FROM <Table Name>
<Filter Conditions > -- Optional
<Group By and Having> - Optional
ORDER BY
<Column 1> <ASC or DESC>,
<Column 2> <ASC or DESC>,
.......
<Column N> <ASC or DESC>,
You Can Either Give the Column Names or the Ordinal Position of the Column in the Select List.
For Example :
SELECT
EmpId,
FirstName,
LastName,
Age,
ContactNumber
FROM Employee
ORDER BY
FirstName,
Age
Can Also be written as
SELECT
EmpId,
FirstName,
LastName,
Age,
ContactNumber
FROM Employee
ORDER BY
2,4
in the second one, I'm giving the Ordinal position of Columns FirstName and Age instead of specifying the Column Name.
This approach is more useful when you have 2 columns with the Same Name in your Resultset.
Example :
SELECT
EmpId,
*
ContactNumber
FROM Employee
ORDER BY
EmpId
The above will give you the following error
Msg 209, Level 16, State 1, Line 5 Ambiguous column name 'EmpId'.
So Instead you can say
SELECT
EmpId,
*
ContactNumber
FROM Employee
ORDER BY
1

Answer 2

You can get and learn in details from the below query. Multiple column OrderBy is useful when similar values are present in table.
Create Table Orders (Id int, ProdName Varchar(20))
insert into Orders Values (1, 'A'), (4, 'C'), (2, 'B'), (3, 'E'), (4, 'G'), (5, 'D'), (6, 'F'), (7, 'G')
Select * from Orders
order by 1 -- Order By Id Ascending
Select * from Orders
order by 1 desc -- Order By Id Descending
Select * from Orders
order by 2 -- Order By Name Ascending
Select * from Orders
order by 2 desc -- Order By Name Descending
Select * from Orders
order by 1, 2 -- Order By Id first and then Name Ascending.
-- It will come same Id first and same name later
Select * from Orders
order by 1 asc, 2 desc --First priority of Id ascending then Name in descending order
Select * from Orders
order by 1, 2 desc
You can find the live demo Live Demo Here