如何获取在SQL中给定行具有空值的列数？

一种方法是使用case和+：

select t.*,
       ( (case when col1 is not null then 1 else 0 end) +
         (case when col2 is not null then 1 else 0 end) +
         (case when col3 is not null then 1 else 0 end) +
         (case when col4 is not null then 1 else 0 end) +
         (case when col5 is not null then 1 else 0 end) +
         (case when col6 is not null then 1 else 0 end) +
         (case when col7 is not null then 1 else 0 end)
        ) as cnt_not_nulls_in_row 
from t;

在MySQL中，可以简化为：

select t.*,
       ( (col1 is not null ) +
         (col2 is not null ) +
         (col3 is not null ) +
         (col4 is not null ) +
         (col5 is not null ) +
         (col6 is not null ) +
         (col7 is not null ) 
        ) as cnt_not_nulls_in_row 
from t;