MySQL

Question

长期以来我一直使用这种方法来排序我的列表（对于 html selects）：

SELECT '' AS ID, '' AS Name UNION 
SELECT ID, Name FROM (SELECT ID, Name FROM myTable ORDER BY Name) AS myTableTmp

但在更新到新的 MySQL(MariaDB) 版本后我发现，这种排序不再有效。就像这里解释的那样，它与 SQL 标准冲突：mysql - order by inside subquery

获得所需订单的最佳做法是什么？或者我应该使用简单的方法，并将 LIMIT 65000 添加到嵌套查询中？

编辑：

嗯，我原来的例子不够精确，所以人们可能会误解我。这是更正的示例：

CREATE TABLE IF NOT EXISTS `myTable` (
  `ID` int(11) NOT NULL AUTO_INCREMENT,
  `Name` varchar(120) DEFAULT NULL,
  PRIMARY KEY (`ID`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=4 ;


INSERT INTO `myTable` (`ID`, `Name`) VALUES
(1, 'Banana'),
(2, 'Apple'),
(3, NULL);

如果我select旧版本：

SELECT '0' AS ID, '-' AS Name UNION 
SELECT ID, Name FROM (SELECT ID, Name FROM myTable ORDER BY Name) AS myTableTmp

我得到：

0   -
3   NULL
2   Apple
1   Banana

如何在新的 MySQL 版本中获得相同的结果？

Answer 1

否则你可以把订单移到外面：

SELECT 
    ID, Name
FROM
    (SELECT '' AS ID, '' AS Name UNION SELECT 
        ID, Name
    FROM
        yourTable) AS yourTableTmp
ORDER BY Name;

Answer 2

您可以使用 ORDER BY CASE ... END 更改默认排序行为以获得预期结果。

工作原理

所有“-”值在 ORDER BY
中的位置为“1” 所有 NULL 值都在 ORDER BY
中获得位置“2” 所有名称都获得位置“3+”并按字母排序。

查询

SELECT '0' AS ID, '-' AS Name UNION 
SELECT ID, Name FROM (
  SELECT
     ID
   , Name
  FROM
   myTable
) AS myTableTmp
ORDER BY
 CASE 
  WHEN 
   Name = '-'
  THEN
   1
  WHEN 
   Name IS NULL
  THEN
   2
  ELSE 
   Name
 END

观看演示 https://www.db-fiddle.com/f/xcy45sUEDKN9gJhNpVqoHd/2

But what if someone put name '-' in table? i may get the wrong id in that case...

查询

SELECT
   '0' AS ID
 , '-' AS Name
 , 0 AS position

UNION

SELECT
   ID
 , Name
 , CASE
     WHEN 
      Name IS NULL
     THEN 
      2
     ELSE
      3
   END AS position
FROM (
   SELECT
       ID
     , Name
   FROM
    myTable 
) AS myTableTmp

ORDER BY 
   position
 , name ASC

观看演示 https://www.db-fiddle.com/f/xcy45sUEDKN9gJhNpVqoHd/7

Answer 3

我想，最干净的 SQL 目前唯一的解决方案如下 Using union and order by clause in mysql

SELECT ID, Name FROM (
SELECT '0' AS ID, '-' AS Name, 1 AS Rank UNION 
SELECT ID, Name, 2 AS Rank FROM myTable
) AS myTableTmp ORDER BY Rank, Name

MySQL - ORDER BY 与 UNION 的一部分

MySQL - ORDER BY with part of UNION

union

sql-order-by

mariadb