How to generate column based on order id in sql

Question

I have two tables: customerTable and orderTable that are shown below. I need to generate order column dynamically.

CustomerTable

custId CustName
01     Suresh
02     Ramesh

OrderTable

custId  OrderId 
01      011
01      012

need output as like :

custId Order1 Order2
01     011    012

Here if order is multiple times for each customer then columns will be added dynamically.

If custId = 01 has 011,012,013,014...... has many order then table will be like

custId order1  order2 order3 order4 order5 order6 ...... many oder N columns 
01     011       012   013   014    015    06     ....... 0N..   

Answer 1

What you are looking for is called pivoting. See the documentation .

A simple example taken from the link above:

USE AdventureWorks2008R2;
GO
SELECT
    DaysToManufacture,
    AVG(StandardCost) AS AverageCost
FROM Production.Product
GROUP BY DaysToManufacture;

Results in:

DaysToManufacture | AverageCost
----------------------------------------
0                 | 5.0885
1                 | 223.88
2                 | 359.1082
4                 | 949.4105

These are rows in the source table grouped, no pivoting done yet. By pivoting, you turn the values of the rows in column #1 into columns, and the values of the rows in column #2 get 'rotated' and appear as one row. The SQL to do that is the following:

-- Pivot table with one row and five columns
SELECT
    'AverageCost' AS Cost_Sorted_By_Production_Days, 
    [0],
    [1],
    [2],
    [3],
    [4]
FROM
(
    SELECT
        DaysToManufacture,
        StandardCost 
    FROM
        Production.Product
) AS SourceTable
PIVOT
(
    AVG(StandardCost)
    FOR DaysToManufacture IN
    (
        [0],
        [1],
        [2],
        [3],
        [4]
    )
) AS PivotTable;

This results in output such as:

Cost_Sorted_By_Production_Days | 0      | 1      | 2        | 3    | 4
-----------------------------------------------------------------------------
AverageCost                    | 5.0885 | 223.88 | 359.1082 | NULL | 949.4105

Answer 2

Do this dynamically like this:

declare @sql as nvarchar(max)
declare @cols as nvarchar(max)

set @cols = STUFF((SELECT distinct ',' + QUOTENAME(c.OrderId)
            FROM OrderTable c
            order by 1
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'');

set @sql = STUFF((SELECT ',' + QUOTENAME(OrderId) + ' as Order' + convert(varchar,row_number() over (order by OrderId))
            from (
                select distinct OrderId 
                FROM OrderTable
            ) t
            order by 1
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'');

set @sql = 'SELECT custId, ' + @sql + ' from 
            (
                select *
                from OrderTable
           ) x
            pivot 
            (
                 max(OrderId)
                for OrderId in (' + @cols + ')
            ) p '
exec(@sql)

Produces:

To be noted here is that, it works correctly for one custId as the columns are aligned based on the the OrderId in the pivoted result.