Unpivoting With APPLY

I have a post on using the APPLY operator to unpivot data:

This code works, but if you have dozens of years, it gets messy writing those case statements and you’re a bit more likely to make a mistake when refactoring code. Here’s a simpler version using CROSS APPLY:

1
2
3
4
5
6
7
8
9
10
11
SELECT
    s.Product,
    y.[Year],
    y.Quantity,
    y.[Value]
FROM #Sales s
    CROSS APPLY (VALUES
        (2013, [Qty2013], [Val2013]),
        (2014, [Qty2014], [Val2014]),
        (2015, [Qty2015], [Val2015])
    ) y([Year], Quantity, [Value]);

It’s a little easier to read than the other version, and adding additional years is pretty straightforward.  That makes for a great tip when you’re trying to refactor poorly-thought-out tables or bring into your system potentially well-thought-out flat files.

APPLY is an elegant solution to so many different classes of problem.

Related Posts

Converting Binary To Hex With T-SQL

Dave Mason uses STRING_SPLIT to convert binary values to their hex equivalents: I started pondering it for a bit and began to wonder if I could use the new for SQL Server 2016 STRING_SPLIT function to convert a binary string to decimal. The thought process was to split the string into rows of CHAR(1) values, along with an in-string character […]

Read More

Faster Scalar Functions In SQL Server 2019

Brent Ozar looks at improvements the SQL Server team has made to scalar functions in 2019: My database has to be in 2019 compat mode to enable Froid, the function-inlining magic. Run the same query again, and the metrics are wildly different: Runtime: 4 seconds CPU time: 4 seconds Logical reads: 3,247,991 (which still sounds bad, […]

Read More

Categories

July 2016
MTWTFSS
« Jun Aug »
 123
45678910
11121314151617
18192021222324
25262728293031