Extract data from json inside mysql field - mysql

Question

I've got a a table with rows, and one of the rows has a field with data like this
{"name":"Richard","lastname":null,"city":"Olavarria","cityId":null}
And i want to select all the distinct "city" values i've got. Only using mysql server.
Is it possible? I'm trying with something like this
SELECT id FROM table_name WHERE field_name REGEXP '"key_name":"([^"]*)key_word([^"]*)"';
But i can't make the regexp work
Thanks in advance

Answer 1

MySQL has got support for JSON in version 5.7.7
http://mysqlserverteam.com/json-labs-release-native-json-data-type-and-binary-format/
You will be able to use the jsn_extract function to efficiently parse your JSON string.
If you have an older version and you want to solve it purely in mysql then I am afraid you have to treat it as a string and cut the value out of it (just normal string functions or use regular expressions)
This is not elegant but it will work
http://sqlfiddle.com/#!9/97cfd/14
SELECT
DISTINCT(substring(jsonfield, locate('"city":',jsonfield)+8,
locate('","', jsonfield, locate('"city":',jsonfield))-locate('"city":',jsonfield)-8)
)
FROM
ForgeRock

Answer 2

I have wrapped this into a stored function for those constrained to MySQL <5.7.7:
CREATE FUNCTION `json_extract_string`(
p_json text,
p_key text
) RETURNS varchar(40) CHARSET latin1
BEGIN
SET #pattern = CONCAT('"', p_key, '":"');
SET #start_i = LOCATE(#pattern, p_json) + CHAR_LENGTH(#pattern);
if #start_i = CHAR_LENGTH(#pattern) then
SET #end_i = 0;
else
SET #end_i = LOCATE('"', p_json, #start_i) - #start_i;
end if;
RETURN SUBSTR(p_json, #start_i, #end_i);
END
Note this only works with string values but is a bit more robust than #DmitryK's answer, in that it returns an empty string if the key is not found and the key can be anywhere in the JSON string.

Answer 3

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} |
+-----+-----------+--------------------------------------+
To Select each JSON fields , run this query :
SELECT
id, client_id,
json_extract(service_values, '$.quota') AS quota,
json_extract(service_values, '$.data_transfer') AS data_transfer
FROM client_services;
So the output will be :
+-----+-----------+----------------------+
| id | client_id | quota | data_transfer|
+-----+-----------+----------------------+
| 100 | 1000 | 1 | 160000 |
| 101 | 1000 | 2 | 800000 |
| 102 | 1000 | 3 | 70000 |
| 103 | 1001 | 1 | 97000 |
| 104 | 1001 | 2 | 1760 |
| 105 | 1002 | 2 | 1060 |
+-----+-----------+----------------------+
NOW, if you want lets say DISTINCT quota , then run this query :
SELECT
distinct( JSON_EXTRACT(service_values, '$.quota')) AS quota
FROM client_services;
So this will result into your desired output :
+-------+
| quota |
+-------+
| 1 |
| 2 |
| 3 |
+-------+
hope this helps!

Answer 4

See MariaDB's Dynamic Columns.
Also, search this forum for [mysql] [json]; the topic has been discussed often.

Answer 5

This may be a little late, but the accepted answer didn't work for me. I used SUBSTRING_INDEX to achieve the desired result.
SELECT
ID, SUBSTRING_INDEX(SUBSTRING_INDEX(JSON, '"mykey" : "', -1), '",', 1) MYKEY
FROM MY_TABLE;
Hope this helps.