MySQL - Search JSON data column - mysql

Question

I have a MySQL database column that contains JSON array encoded strings. I would like to search the JSON array where the "Elapsed" value is greater than a particular number and return the corresponding TaskID value of the object the value was found. I have been attempting to use combinations of the JSON_SEARCH, JSON_CONTAINS, and JSON_EXTRACT functions but I am not getting the desired results.
[
{
"TaskID": "TAS00000012344",
"Elapsed": "25"
},
{
"TaskID": "TAS00000012345",
"Elapsed": "30"
},
{
"TaskID": "TAS00000012346",
"Elapsed": "35"
},
{
"TaskID": "TAS00000012347",
"Elapsed": "40"
}
]
Referencing the JSON above, if I search for "Elapsed" > "30" then 2 records would return
'TAS00000012346'
'TAS00000012347'
I am using MySQL version 5.7.11 and new to querying json data. Any help would be appreciated. thanks

Answer 1

With MySQL pre-8.0, there is no easy way to turn a JSON array to a recordset (ie, function JSON_TABLE() is not yet available).
So, one way or another, we need to manually iterate through the array to extract the relevant pieces of data (using JSON_EXTRACT()). Here is a solution that uses an inline query to generate a list of numbers ; another classic approchach is to use a number tables.
Assuming a table called mytable with a column called js holding the JSON content:
SELECT
JSON_EXTRACT(js, CONCAT('$[', n.idx, '].TaskID')) TaskID,
JSON_EXTRACT(js, CONCAT('$[', n.idx, '].Elapsed')) Elapsed
FROM mytable t
CROSS JOIN (
SELECT 0 idx
UNION ALL SELECT 1
UNION ALL SELECT 2
UNION ALL SELECT 3
) n
WHERE JSON_EXTRACT(js, CONCAT('$[', n.idx, '].Elapsed')) * 1.0 > 30
NB: in the WHERE clause, the * 1.0 operation is there to force the conversion to a number.
Demo on DB Fiddle with your sample data:
| TaskID | Elapsed |
| -------------- | ------- |
| TAS00000012346 | 35 |
| TAS00000012347 | 40 |

Answer 2

Yes , you can definitely to it using JSON_EXTRACT() function in mysql.
lets take a table that contains JSON (table client_services here) :
+-----+-----------+--------------------------------------+
| id | client_id | service_values |
+-----+-----------+------------+-------------------------+
| 100 | 1000 | { "quota": 1,"data_transfer":160000} |
| 101 | 1000 | { "quota": 2,"data_transfer":800000} |
| 102 | 1000 | { "quota": 3,"data_transfer":70000} |
| 103 | 1001 | { "quota": 1,"data_transfer":97000} |
| 104 | 1001 | { "quota": 2,"data_transfer":1760} |
| 105 | 1002 | { "quota": 2,"data_transfer":1060} |
+-----+-----------+--------------------------------------+
And now lets say we want client_id for all who have quota>1 , then use this query :
SELECT
id,client_id,
JSON_EXTRACT(service_values, '$.quota') AS quota
FROM client_services
WHERE JSON_EXTRACT(service_values, '$.quota') > 1;
And hence it will result into :
+-----+-----------+-------+
| id | client_id | quota |
+-----+-----------+--------
| 101 | 1000 | 2 |
| 102 | 1000 | 3 |
| 104 | 1001 | 2 |
| 105 | 1002 | 2 |
+-----+-----------+-------+
hope this helps!