从MySQL JSON数组获取不同的值 [英] Get distinct values from MySQL JSON array

问题描述

我得到了一个MySQL数据表，其中的JSON列包含值列表:

I got a MySQL data Table, with a JSON Column containing a list of Values:

CONSTRAINT_TABLE

CONSTRAINT_TABLE

 ID | CONSTRAINT_TYPE | CONSTRAINT_VALUES
----+-----------------+--------------------------------
 '2'| 'testtype'      |'[801, 751, 603, 753, 803]'
 ...| ...             | ...

我想要的是一个独特的，用逗号分隔的JSON值列表.我用group_concat尝试过，但是它适用于数组，而不是单个值.

What I want to have is a distinct, comma-seperated List of JSON-Values. I tried it with group_concat, but it applys to the arrays, not the single values.

SELECT group_concat(distinct constraint_values->>'$') 
FROM constraint_table c 
WHERE c.constraint_type = "testtype";

实际结果:

[801, 751, 603, 753, 803],[801, 751],[578, 66, 15],...

我的目标结果:

801, 751, 603, 753, 803, 578, 66, 15 ...

无重复.因为行也很好.

without duplicates. As rows would be nice, too.

想法，有人吗?

推荐答案

对不起，请您提前告知我，但我遇到过类似的问题.解决方案是:JSON_TABLE()自MySQL 8.0起可用.

Sorry for necromancing, but I've encountered similar issue. The solution is: JSON_TABLE() available since MySQL 8.0.

首先，将行中的数组合并为一个单行数组.

First, merge the arrays in rows into one-row single array.

select concat('[',         -- start wrapping single array with opening bracket
    replace(
        replace(
            group_concat(vals),  -- group_concat arrays from rows
            ']', ''),            -- remove their opening brackets
        '[', ''),              -- remove their closing brackets
    ']') as json             -- finish wraping single array with closing bracket
from (
  select '[801, 751, 603, 753, 803]' as vals
  union select '[801, 751]'
  union select '[578, 66, 15]'
) as jsons;

# gives: [801, 751, 603, 753, 803, 801, 751, 578, 66, 15]

第二，使用json_table将数组转换为行.

Second, use json_table to convert the array into rows.

select val
from (
    select concat('[',
        replace(
            replace(
                group_concat(vals),
                ']', ''),
            '[', ''),
        ']') as json
    from (
      select '[801, 751, 603, 753, 803]' as vals
      union select '[801, 751]'
      union select '[578, 66, 15]'
    ) as jsons
) as merged
join json_table(
    merged.json,
    '$[*]' columns (val int path '$')
) as jt
group by val;

# gives...
801
751
603
753
803
578
66
15

请参见 https://dev.mysql.com/doc/refman/8.0/zh-CN/json-table-functions.html#function_json-table

注意group by val以获得不同的值.您还可以order它们以及所有内容...

Notice group by val for getting distinct values. You can also order them and everything...

或者您可以在不使用group by指令(！)的情况下使用group_concat(distinct val)获得单行结果.

Or you can use group_concat(distinct val) without the group by directive (!) to get one-line result.

甚至cast(concat('[', group_concat(distinct val), ']') as json)以获得正确的json数组:[15, 66, 578, 603, 751, 753, 801, 803].

Or even cast(concat('[', group_concat(distinct val), ']') as json) to get a proper json array: [15, 66, 578, 603, 751, 753, 801, 803].

阅读我的使用MySQL作为JSON存储的最佳做法:)

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