Question

I have a query that UNION‘s two somewhat similar datasets, but they both have some columns that are not present in the other (i.e., the columns have NULL values in the resulting UNION.)

The problem is, I need to ORDER the resulting data using those columns that only exist in one or the other set, to get the data in a friendly format for the software-side.

For example: Table1 has fields ID, Cat, Price. Table2 has fields ID, Name, Abbrv. The ID field is common between the two tables.

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My query looks like something like this:

SELECT t1.ID, t1.Cat, t1.Price, NULL as Name, NULL as Abbrv FROM t1 
UNION 
SELECT t2.ID, NULL as Cat, NULL as Price, t2.Name, t2.Abbrv FROM t2 
ORDER BY Price DESC, Abbrv ASC 

The ORDER BY is where I’m stuck. The data looks like this:

100   Balls     1.53                       
200   Bubbles   1.24                       
100                     RedBall    101RB   
100                     BlueBall   102BB   
200                     RedWand    201RW   
200                     BlueWand   202BW   

…but I want it to look like this:

100   Balls     1.53                       
100                     RedBall    101RB   
100                     BlueBall   102BB   
200   Bubbles   1.24                       
200                     RedWand    201RW   
200                     BlueWand   202BW   

I’m hoping this can be done in T-SQL.

Answer 1

Select ID, Cat, Price, Name, Abbrv
From
(SELECT t1.ID, t1.Cat, t1.Price, t1.Price AS SortPrice, NULL as Name, NULL as Abbrv 
FROM t1
UNION
SELECT t2.ID, NULL as Cat, NULL as Price, t1.Price as SortPrice, t2.Name, t2.Abbrv 
   FROM t2
   inner join t1 on t2.id = t1.id
) t3
ORDER BY SortPrice DESC, Abbrv ASC

Somehow you have to know the data in table 2 are linked to table 1 and share the price. Since the Null in abbrv will come first, there is no need to create a SortAbbrv column.