SQL - 如何对案例语句进行分类？

Question

In this sample dataset, I have some Colors : "Red" and "Blue" and some Fruit : "Apple" and "Grapes" associated with a person/name.

My goal is to add a column for each of these groupings, called "Colors" and Fruit . These newly added columns would count +1 whenever the value is > 0 for each of their respective grouping.

For example if either "Red" or "Blue" contain a value > 0, we will add +1 to Colors . For John Smith, since both the Red and Blue columns contain a value > 0, the Colors column will be 2. Here is the expected output:

I know case statements can add 1 or 0, but how do we do this when we have 2 columns per grouping?

Answer 1

You do not need in CASE.

SELECT blue, red, (blue > 0) + (red > 0) colors,
       apple, grapes, (apple > 0) + (grapes > 0) fruit
FROM source_table

The values in source table shouldn't be NULL.

Answer 2

SELECT
  *,
  ((CASE WHEN apple > 0 THEN 1 ELSE 0 END) + (CASE WHEN WHEN grapes > 0 THEN 1 ELSE 0 END)) as fruit,
  ((CASE WHEN red > 0 THEN 1 ELSE 0 END) + (CASE WHEN blue > 0 THEN 1ELSE 0 END)) as colors
from table

Answer 3

assuming the source data is in a pivoted state

with cte as (
select 'john' as name, 2 as blue, 3 as red, 2 as apple, 4 as grape union all
select 'tom', 0 , 8, 0, 0
)
select
      name
    , blue
    , red
    , coalesce((blue > 0),0) 
      + coalesce((red > 0),0)
      as colours
    , apple
    , grape
    , coalesce((apple > 0),0) 
      + coalesce((grape > 0),0)
      as fruits
from cte

name | blue | red | colours | apple | grape | fruits
:--- |  ---: |  --: |  ------: |  ----: |  ----: |  -----: 
john | 2 |  3 |  2 |  2 |  4 |  2 
tom | 0 |  8 |  1 |  0 |  0 |  0 

db<>fiddle here