SELECT duration,id FROM `tickets` WHERE duration !=""

SELECT duration,id FROM `tickets` WHERE duration !=""

哪里的coalesce(所有的列)不是空的

你可以过滤掉特定列中包含NULL值的行:

SELECT col1, col2, ..., coln
FROM yourtable
WHERE somecolumn IS NOT NULL

如果你想过滤掉任何列中包含null的行，那么试试这个:

SELECT col1, col2, ..., coln
FROM yourtable
WHERE col1 IS NOT NULL
AND col2 IS NOT NULL
-- ...
AND coln IS NOT NULL

更新:根据你的评论，也许你想要这个?

SELECT * FROM
(
    SELECT col1 AS col FROM yourtable
    UNION
    SELECT col2 AS col FROM yourtable
    UNION
    -- ...
    UNION
    SELECT coln AS col FROM yourtable
) T1
WHERE col IS NOT NULL

我同意Martin的观点，如果你需要这样做，那么你可能应该改变你的数据库设计。

Mysql不是空的连接和选择，插入，删除和逻辑操作符像或，不是

Using IS NOT NULL On Join Conditions

 SELECT * FROM users 
 LEFT JOIN posts ON post.user_id = users.id 
 WHERE user_id IS NOT NULL;

 Using IS NOT NULL With AND Logical Operator

 SELECT * FROM users 
 WHERE email_address IS NOT NULL 
 AND mobile_number IS NOT NULL;

Using IS NOT NULL With OR Logical Operator

 SELECT * FROM users 
 WHERE email_address IS NOT NULL 
 OR mobile_number IS NOT NULL;

你应该使用IS NOT NULL。(比较运算符=和<>都在表达式的两侧给出UNKNOWN和NULL。)

SELECT * 
FROM table 
WHERE YourColumn IS NOT NULL;

为了完整起见，我要提一下，在MySQL中，你也可以对空安全的相等操作符求反，但这不是标准SQL。

SELECT *
FROM table 
WHERE NOT (YourColumn <=> NULL);

编辑以反映评论。听起来您的表可能不是第一种正常形式，在这种情况下，更改结构可能会使您的任务更容易。不过，还有一些其他的方法……

SELECT val1 AS val
FROM  your_table
WHERE val1 IS NOT NULL
UNION ALL
SELECT val2 
FROM  your_table
WHERE val2 IS NOT NULL
/*And so on for all your columns*/

上述方法的缺点是它对表进行多次扫描，每列一次。这也许可以通过下面来避免，但我还没有在MySQL中测试过。

SELECT CASE idx
         WHEN 1 THEN val1
         WHEN 2 THEN val2
       END AS val
FROM   your_table
        /*CROSS JOIN*/
       JOIN (SELECT 1 AS idx
                   UNION ALL
                   SELECT 2) t
HAVING val IS NOT NULL  /*Can reference alias in Having in MySQL*/