Regrouping table-CodePudding

I have a table like below:

NAME1 | NAME2 | NUM
------------------------
AAA   | D1    | 0       
AAA   | D2    | 9
BBB   | D1    | 3
AAA   | D4    | 2
CCC   | D2    | 10

I wish to regroup the table to look like this:

NAME1 |D1| D2| D3| D4
------------------------
AAA   | 0| 9 | -1| 2
BBB   | 3| -1| -1|-1
CCC   |-1| 10| -1|-1

If a NAME1-Dx combination is missing (for x=1,...,4) in the first table, then I want to write the value -1 in the respective Dx field of the second table.

CodePudding user response：

Use a pivot query, with the help of COALESCE() to replace missing values with -1.

SELECT
    NAME1,
    COALESCE(MAX(CASE WHEN NAME2 = 'D1' THEN NUM END), -1) AS D1,
    COALESCE(MAX(CASE WHEN NAME2 = 'D2' THEN NUM END), -1) AS D2,
    COALESCE(MAX(CASE WHEN NAME2 = 'D3' THEN NUM END), -1) AS D3,
    COALESCE(MAX(CASE WHEN NAME2 = 'D4' THEN NUM END), -1) AS D4
FROM yourTable
GROUP BY NAME1;