SQL 查询表的每一列中非 null 值的计数？

Question

I can find the count of non null values by typing each column name, but is there a way to write it without manually typing the column names as I have 100+ columns in my table.

select 'col1Name', count(col1Name) from table where col1Name is null
union
select 'col2Name', count(col2Name) from table where col2Name is null
union ...
select 'col20Name', count(col20Name) from table where col20Name is null

Answer 1

You can use a case operation here

select 
  sum(case when a is null then 1 else 0 end) A,
  sum(case when b is null then 1 else 0 end) B,
  sum(case when c is null then 1 else 0 end) C
from T