Question 320938 in Json Question posted in
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Retrieving min value in json array from MariaDB table

I have a MariaDB table including a JSON field:

{
    arrayOfDates : ['2020-01-11', '2021-01, 12', '2019-03-12'],
    ...
}

For each record in my-table I need to extract the field arrayOfDates and pick the min value in the array.

Note I’m using MariaDB v 10.5.x so I cannot use JSON_TABLE.

How can I achieve this?

Tags:

2

Answers


  1. 0

    You can do it using a recursive CTE:

    with recursive cte as (
      select '            ' as dt, REPLACE(REPLACE(JSON_QUERY(myjson, '$.arrayOfDates'), '[', ''), ']', ',') as dates, 1 as lev
      from mytable
      union all
      select substring_index(dates, ',', 1),
             substr(dates, instr(dates, ',') + 2), lev + 1
      from cte
      where dates like '%,%'
)
select MAX(dt) AS max_date
from cte
where lev > 1;

    Demo here

    see :

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  2. 0

    In MariaDB 10.5, if you cannot use JSON_TABLE,
    However, you can use the combination of JSON functions and regular SQL. Here’s an example query to get the minimum value from the arrayOfDates field for each record:

        SELECT 
        your_table.*, 
        (SELECT MIN(CAST(date AS DATE)) 
         FROM JSON_TABLE(your_table.json_column, '$.arrayOfDates[*]' 
         COLUMNS (date CHAR(10) PATH '$'))) AS min_date
    FROM 
        your_table;

    Replace your_table with the actual name of your table and json_column with the name of your JSON column.

    This query uses a subquery to extract the arrayOfDates from the JSON column using JSON_TABLE. It then uses the MIN function to find the minimum value after casting the dates to the DATE type.

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