I have a JSON field in mysql for tags like so
[
{"id": 138001, "tag": "Travel"},
{"id": 138002, "tag": "Holidays"}
]
and I want to retrieve it as 'Travel Holidays'
I can get the values in the a json array format:
["Travel", "Holidays"]
with the current statement,
SELECT JSON_EXTRACT(post_tags, '$[*].tag') AS tags FROM posts WHERE post_id = 646745;
but I'm not sure if there is a way to flatten the array into a single string separated by spaces, is it possible?
My reason for doing this, is that sphinx search indexes the tags field also and you can get the id values in the index which isn't desired at all
Well you could just let sphinx index ["Travel", "Holidays"] directly.
As per charset_table rules, the [, " and , will just be 'ignored' (more technically treated as separators and collapsed away)
Also not familiar with it, but maybe JSON_UNQUOTE could work? Don't know if it can collapse arrays.
Related
I have some JSON data in Redshift table of type character varying. An example entry is:
[{"value":["*"], "key":"testData"}, {"value":"["GGG"], key: "differentData"}]
I want to return vales based on keys, how can i do this? I'm attempting to do something like
json_extract_path_text(column, 'value') but unfortunately it errors out. Any ideas?
So the first issue is that your string isn't valid JSON. There are mismatched and missing quotes. I think you mean:
[{"value":["*"], "key":"testData"}, {"value":["GGG"], "key": "differentData"}]
I don't know if this is a data issue or a transcription error but these functions won't work unless the json text is valid.
The next thing to consider is that at the top level this json is an array so you will need to use json_extract_array_element_text() function to pick up an element of the array. For example:
json_extract_array_element_text('json string', 0)
So putting this together we can extract the first "value" with (untested):
json_extract_path_text(
json_extract_array_element_text(
'[{"value":["*"], "key":"testData"}, {"value":["GGG"], "key": "differentData"}]', 0
), 'value'
)
Should return the string ["*"].
The data in the column looks like the below:
{
"activity": {
"token": "e7b64be4-74d4-7a6d-a74b-xxxxxxx",
"route": "http://example.com/enroll/confirmation",
"url_parameters": {
"Success": "True",
"ContractNumber": "003992314W",
"Barcode": "1908Y10Z",
"price": "8.99"
},
"server_info": {
"cookie": [
"_ga=xxxx; _fbp=xxx; _hjid=xxx; XDEBUG_SESSION=XDEBUG_ECLIPSE;"
],
"upgrade-insecure-requests": [
"1"
],
},
"campaign": "Unknown/None",
"ip": "192.168.10.1",
"entity": "App\\Models\\User",
"entity_id": "1d9f3066-13ce-4659-b10d-xxxxx",
},
"time": "2021-05-21 20:15:02"
}
My code that I am using is below:
SELECT *
FROM websote.stored_events
WHERE JSON_EXTRACT(event_properties, '$.route') = 'http://example.com/enroll/confirmation'
ORDER BY created_at DESC LIMIT 500;
The code works on the other the json values just not the url ones. I've tried escaping the values in MySQL like the below:
SELECT *
FROM websote.stored_events
WHERE JSON_EXTRACT(event_properties, '$.route') = 'http:///example.com//enroll//confirmation'
ORDER BY created_at DESC LIMIT 500;
But still no luck. Any help on this would be appreciated!
Route is a nested property; I would have expected the path to be
JSON_EXTRACT(event_properties, '$.activity.route')
Your example data isn't valid JSON. You can't have a comma after the last element in an object or array:
"entity_id": "1d9f3066-13ce-4659-b10d-xxxxx",
},
^ here
If I remove that and other similar cases, I can test your data inserts into a JSON column and I can extract the object element you described:
mysql> select json_extract(event_properties, '$.activity.route') as route from stored_events;
+------------------------------------------+
| route |
+------------------------------------------+
| "http://example.com/enroll/confirmation" |
+------------------------------------------+
Note the value is returned with double-quotes. This is because it's returned as a JSON document, a scalar string. If you want the raw value, you have to unquote it:
mysql> select json_unquote(json_extract(event_properties, '$.activity.route')) as route from stored_events;
+----------------------------------------+
| route |
+----------------------------------------+
| http://example.com/enroll/confirmation |
+----------------------------------------+
If you want to search for that value, you would have to do a similar expression:
select * from stored_events
where json_unquote(json_extract(event_properties, '$.activity.route'))
= 'http://example.com/enroll/confirmation'
Searching based on object properties stored in JSON has disadvantages.
It requires complex expressions that force you (and anyone else you needs to maintain your code) to learn a lot of details about how JSON works.
It cannot be optimized with an index. This query will run a table-scan. You can add virtual columns with indexes, but that adds to complexity and if you need to ALTER TABLE to add virtual columns, it misses the point of JSON to store semi-structured data.
The bottom line is that if you find yourself using JSON functions in the WHERE clause of a query, it's a sign that you should be storing the column you want to search as a normal column, not as part of a JSON document.
Then you can write code that is easy to read, easy for your colleagues to maintain, and can be optimized easily with indexes:
SELECT * FROM stored_events
WHERE route = 'http://example.com/enroll/confirmation';
You can still store other properties in the JSON document, but the ones you want to be searchable should be stored in normal columns.
You might like to view my presentation How to Use JSON in MySQL Wrong.
Given JSON like:
[
{
"Serial no": 994,
},
{
"Serial no": 456,
}
]
I know this query will give me an array of all Serial no values, in the order they are in the JSON: $..['Serial no']
I'm not sure exactly what sorting capabilities JSONPath has but I think you can use / and \ to sort - but how are they used to modify my query string in this case? I am only interested doing this in pure JSONPath, not JS or post-query sorting - that's easy, I just want to know if I can avoid it.
This is a source I found suggesting sorting is supported but it might be product-specific?
I'm using http://www.jsonquerytool.com/ to test this
Couchbase queries should support any String for property-name in a filter ( where clause.)
But the query below returns no values for any of the fieldNames "7", "a", "#", "&", "", "?". It does work for values for fieldName a.
Note that I'm using the Java DSL API, not N1ql directly.
OffsetPath statement = select("*").from(i(bucket.name())).where(x(fieldName).eq(x("$t")));
JsonObject placeholderValues = JsonObject.create().put("t", fieldVal);
N1qlQuery q = N1qlQuery.parameterized(statement, placeholderValues);
N1qlQueryResult result = bucket.query(q);
But my bucket does have each of these JsonObjects, including those with unusual property names, as shown by an unfiltered query:
{"a":"a"}
{"#":"a"}
{"&":"a"}
{"":"a"}
{"?":"a"}
How do I escape property names or otherwise support these legal names in queries?
(This question relates to another one, but that is about values and this is about field names.)
The field name is treated as an identifier. So, back-ticks are needed to escape them thus:
select("*").from(i(bucket.name())).where(x("`" + fieldName + "`").eq(x("$value"))
with parameterization of $value, of course
I have a nullable column with the JSON type:
CREATE TABLE mytable (mycolumn JSON);
What I want to do is track events in an array as they come and keep each event in the form of an object inside this array. The desired contents of mycolumn after three events have been pushed into the array would be:
[
{"product": ["book"], "subgenre": ["scifi"], "genre": ["fiction"]},
{"product": ["book"], "subgenre": ["space"], "genre": ["fiction"]},
{"product": ["book"], "genre": ["romance"]},
]
The shape of the objects are irrelevant and unknown (the above are just examples). The only known is that each event will be an object with at least one property. Wether that property is an array, object, scalar, string, or null is unknown.
The column will be null initially and my tests revealed that I need to coalesce it into an array or pushing into it will fail.
The closest I got to making this work was:
UPDATE
mytable
SET
mycolumn = JSON_ARRAY_APPEND (
COALESCE (mycolumn, '[]'),
'$',
(
'{"product": ["book"], "subgenre": ["scifi"], "genre": ["fiction"], "type": ["newrelease"]}'
)
);
The problem is that this query interprets the whole object as a string and I end up with an array of strings instead of an array of objects:
SELECT mycolumn FROM mytable;
[
"{\"product\":[\"book\"],\"subgenre\":[\"scifi\"],\"genre\":[\"fiction\"]}",
"{\"product\":[\"book\"],\"subgenre\":[\"space\"],\"genre\":[\"fiction\"]}",
"{\"product\":[\"book\"],\"genre\":[\"romance\"]}"
]
Looks to me like you want to use something like the JSON_MERGE_PRESERVE function, not JSON_ARRAY_APPEND function.
The latter evaluates the third argument as a value, it doesn't evaluate the third argument as a JSON document.
In the UPDATE statement shown, the spurious parens around the third argument (to JSON_ARRAY_APPEND) have no meaning. That third argument is just a value. The value is a long-ish string that looks like JSON, but in this context, it's just a string.
Reference: https://dev.mysql.com/doc/refman/8.0/en/json-modification-functions.html#function_json-array-append
My suggestion to testing and development of expressions... it is easier and faster to use SELECT statements. Once we have expressions that are returning the expected/desired results, then we can move the expression into an UPDATE statement.
cast('{"product": ["book"], "subgenre": ["scifi"], "genre": ["fiction"], "type": ["newrelease"]}' as json)
This is a similar question:
MySQL append json object to array of json objects