MySQL SELECT DISTINCT 多列

Question

假设我在 MySQL 数据库的表中有列a, b c, d 。 我想要做的是 select 我表中所有这 4 列的不同值（只有不同的值）。 我尝试过类似的东西：

SELECT DISTINCT a,b,c,d FROM my_table;
SELECT DISTINCT a,b,c,d FROM my_table GROUP BY a,b,c,d;

这些都没有奏效。 有人可以在这里帮忙吗？

谢谢

注意我想要a, b, c d列的不同值。 不是价值的独特组合

Answer 1

我知道这个问题太老了，无论如何：

SELECT a, b
FROM mytable
GROUP BY a, b;

这将为您提供所有组合。

Answer 2

这有帮助吗？

select 
(SELECT group_concat(DISTINCT a) FROM my_table) as a,
(SELECT group_concat(DISTINCT b) FROM my_table) as b,
(SELECT group_concat(DISTINCT c) FROM my_table) as c,
(SELECT group_concat(DISTINCT d) FROM my_table) as d

Answer 3

猜测你想要的结果，所以也许这就是你想要的查询

SELECT DISTINCT a FROM my_table
UNION 
SELECT DISTINCT b FROM my_table
UNION
SELECT DISTINCT c FROM my_table
UNION
SELECT DISTINCT d FROM my_table

Answer 4

另一种简单的方法是使用concat()

SELECT DISTINCT(CONCAT(a,b)) AS cc FROM my_table GROUP BY (cc);

Answer 5

您的两个查询都是正确的，应该会给您正确的答案。

我建议使用以下查询来解决您的问题。

SELECT DISTINCT a,b,c,d,count(*) Count FROM my_table GROUP BY a,b,c,d
order by count(*) desc

即添加 count(*) 字段。 这将使您了解使用 group 命令消除了多少行。

Answer 6

这将在所有列中给出 DISTINCT 值：

SELECT DISTINCT value
FROM (
    SELECT DISTINCT a AS value FROM my_table
    UNION SELECT DISTINCT b AS value FROM my_table
    UNION SELECT DISTINCT c AS value FROM my_table
) AS derived

Answer 7

您可以简单地使用它来取回一行，其中包含四个逗号分隔的列表，其中包含所有值。

SELECT
  GROUP_CONCAT(DISTINCT `a`) AS `as`,
  GROUP_CONCAT(DISTINCT `b`) AS `bs`,                
  GROUP_CONCAT(DISTINCT `c`) AS `cs`,                
  GROUP_CONCAT(DISTINCT `d`) AS `ds`
FROM
  `my_table`;

如果您需要逗号以外的其他分隔符，请将SEPARATOR选项添加到GROUP_CONCAT 。

Answer 8

select distinct concat( colA, ' ', colB, ' ', colC ) from tableName;

Answer 9

根据您的回答，我做了同样的事情，但是为了提取 json 列vars ，其中 arrays 的 8 个值全部合并在 1 列中，引号修剪了不同的值。

SELECT DISTINCT TRIM(BOTH '"' FROM T1.`vars`) FROM (
    SELECT JSON_EXTRACT(`vars`, '$[1]') AS `vars` 
         FROM my_table
         WHERE `vars` != '[]'
         UNION 
    SELECT JSON_EXTRACT(`vars`, '$[2]') AS `vars`
         FROM my_table
         WHERE `vars` != '[]'
         UNION 
    SELECT JSON_EXTRACT(`vars`, '$[3]') AS `vars`
         FROM my_table
         WHERE `vars` != '[]'
         UNION 
    SELECT JSON_EXTRACT(`vars`, '$[4]') AS `vars`
         FROM my_table
         WHERE `vars` != '[]'
         UNION 
    SELECT JSON_EXTRACT(`vars`, '$[5]') AS `vars`
         FROM my_table
         WHERE `vars` != '[]'
         UNION 
    SELECT JSON_EXTRACT(`vars`, '$[6]') AS `vars`
         FROM my_table
         WHERE `vars` != '[]'
         UNION 
    SELECT JSON_EXTRACT(`vars`, '$[7]') AS `vars`
         FROM my_table
         WHERE `vars` != '[]'
         UNION 
    SELECT JSON_EXTRACT(`vars`, '$[8]') AS `vars`
         FROM my_table
         WHERE `vars` != '[]'
) T1
WHERE `vars` IS NOT NULL
AND `vars` != 'false';

希望它可以帮助...