How to conditional update field in JSON in MySQL? - mysql

Question

We have Student table which contains JSON in 'jsonData' column(longtext).
We need to change value of "isHandicapped" field in json.
Structure:
{
"data": {
"schoolData": {
"studentListe": [
{
"student": {
"studentId": 111749,
"isHandicapped": false
}
}
],
},
}
}
Old Data: "isHandicapped": false
New Value: "isHandicapped": "NO"
This should be conditional update as for true we need to change value as
Old Data: "isHandicapped": true
New Value: "isHandicapped": "Ja"
Primary field of table is ID.
I got following SQL Query for same but unable to understand how to add conditional update that if value is true put Ja else NO:
update Student
set data = JSON_SET(data, "'$."data"."schoolData"."studentListe"[*]."isHandicapped", "?")
where id = 2;

Answer 1

Here's how you would extract that field:
select json_extract(data, '$.data.schoolData.studentListe[*].student.isHandicapped') from Student;
+-------------------------------------------------------------------------------+
| json_extract(data, '$.data.schoolData.studentListe[*].student.isHandicapped') |
+-------------------------------------------------------------------------------+
| [false] |
+-------------------------------------------------------------------------------+
You can use JSON_SET() to set a value for a specific array member 0:
update student set data = json_set(data, '$.data.schoolData.studentListe[0].student.isHandicapped', 'NO');
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
select json_extract(data, '$.data.schoolData.studentListe[*].student.isHandicapped') from Student;
+-------------------------------------------------------------------------------+
| json_extract(data, '$.data.schoolData.studentListe[*].student.isHandicapped') |
+-------------------------------------------------------------------------------+
| ["NO"] |
+-------------------------------------------------------------------------------+
But you can't use the * wildcard to update all array members:
update student set data = json_set(data, '$.data.schoolData.studentListe[*].student.isHandicapped', '"NO"');
ERROR 3149 (42000): In this situation, path expressions may not contain the * and ** tokens or an array range.
I see a lot of questions on Stack Overflow these days about selecting or modifying JSON data in MySQL. Usually the answer is:
You shouldn't store data in JSON format if you need to select or update fields within the JSON document.
This type of task is easy to solve if you stored your data in normal tables and columns:
UPDATE StudentListe
SET isHandicapped = 'NO'
WHERE studentId = 2;

Answer 2

The following update statement will do the trick:
UPDATE Student
SET $.isHandicapped= CASE
WHEN JSON_EXTRACT(data, "'$."data"."schoolData"."studentListe"[*]."isHandicapped")='false'
THEN 'NO'
ELSE 'Ja' end
WHERE id=2;