使用動態變量搜索 JSON_ARRAY

Question

是否可以使用變量作為索引而不是硬編碼值來搜索 JSON_ARRAY？

這就是我的意思：

SELECT
t1.*,
t1.tickets->>"$[t1.arr_pos]"
FROM
(
    SELECT
    c.id AS competition_id,
    JSON_ARRAYAGG(t.id) AS tickets,
    COUNT(t.id) AS tickets_sold,
    FLOOR(RAND()*(COUNT(t.id)-0+1)) AS arr_pos
    FROM competitions c
    JOIN tickets t ON t.competition_id = c.id
    WHERE c.end_date = '2021-01-15 15:00:00'
    AND c.tickets_sold > 0
    GROUP BY c.id
) t1

如果我將 t1.arr_pos 更改為一個數字（0、1、2 等），它顯然可以工作，但我需要根據 arr_pos 中包含的內容進行搜索。

Answer 1

您可以使用JSON_SEARCH() function 來確定數組中第一次出現的搜索表達式的索引（在這種情況下，選擇一個 id 值數組）以及one作為第二個參數，然后按此值提取得到想要的結果。

SELECT t1.*, 
       JSON_EXTRACT(t1.tickets,
                    JSON_UNQUOTE(JSON_SEARCH(t1.tickets, 'one', "123")) 
                 -- example id value is 123
       ) AS Result,
       JSON_UNQUOTE(JSON_SEARCH(tickets, 'one', "123")) AS Related_Index
  FROM
  (
   <your subquery>
  )

演示

Answer 2

無法讓 JSON_SEARCH 工作，但工作如下：

SELECT
t1.*,
JSON_EXTRACT(t1.tickets, CONCAT('$[', t1.arr_pos, ']')) AS winning_ticket
FROM
(
    SELECT
    c.id AS competition_id,
    JSON_ARRAYAGG(t.id) AS tickets,
    COUNT(t.id) AS tickets_sold,
    FLOOR(RAND()*(COUNT(t.id))) AS arr_pos
    FROM competitions c
    JOIN tickets t ON t.competition_id = c.id
    WHERE c.end_date = '2021-01-15 15:00:00'
    AND c.tickets_sold > 0
    GROUP BY c.id
) t1