Question

I am looking for some help on designing a simple pivot so that I can link it into other parts of my queries.

My data is like this

Items Table

Below is my table if I run Select * from items

ITEM      Weight    
12345         10    
12345         11    
654321        50    
654321        20    
654321       100

There are hundreds of Items in this table but each item code will only ever have
maximum of 3 weight records each.

I want the desired output

ITEM     Weight_1    Weight_2     Weight_3
12345          10          11         null
654321         50          20          100

Would appreciate any suggestions,
I have played around with pivots but each subsequent item puts the weights into weight 4,5,6,7,etc
instead of starting at weight1 for each item.

Thanks

Update

Below is what I have used so far,

SELECT r.*
FROM   (SELECT 'weight' + CAST(Row_number() OVER (ORDER BY regtime ASC)AS
                               VARCHAR(10))
                      line,
               id,
               weight
        FROM   items it) AS o PIVOT(MIN([weight]) FOR line IN (weight1, weight2,
       weight3)) AS r  

Answer 1

You were almost there! You were only missing the PARTITION BY clause in OVER:

SELECT r.*
FROM   (SELECT 'weight' + CAST(Row_number() OVER (PARTITION BY id ORDER BY
                               regtime ASC)
                                      AS
                                              VARCHAR(10)) line,
               id,
               weight
        FROM   items it) AS o PIVOT(MIN([weight]) FOR line IN (weight1, weight2,
       weight3)) AS r  

When you PARTITION BY by ID, the row numbers are reset for each different ID.

Update

You do not need dynamic pivot, since you will always have 3 weights. But, if you ever need dynamic number of columns, take a look at some of the examples here:

• SQL Server PIVOT perhaps?
• Pivot data in T-SQL
• How do I build a summary by joining to a single table with SQL Server?