mysql - 如何在 select 语句中选择 count()

Question

经过几个小时的尝试，我终于明白我需要帮助。

我试图从 TableA 中选择一行，然后计算该行不为空的单元格的数量。

我知道这是错误的，但它传达了我的意图

SELECT COUNT(colName), 
    (SELECT (column1, column2, column3, column4) AS colName 
     FROM TableA 
     WHERE location= location) 
AS colCount
FROM TableA  
WHERE colName IS NOT NULL  

Answer 1

<强> SQL DEMO

SELECT id, 
       (`column1` IS NOT NULL) + 
       (`column2` IS NOT NULL) + 
       (`column3` IS NOT NULL) as notnull
FROM Table1