Suppose that I have a MySQL table with a JSON field that contains only numbers, like this (note: using MySQL 8):
CREATE TABLE my_table (
id int,
some_field json
);
Sample data:
id: 1
some_field: [1, 2, 3, 4, 5]
id: 2
some_field: [3, 6, 7]
id: 3
some_field: null
I would like to merge another array of data with the existing values of some_field, while removing duplicates. I was hoping that this might work, but it didn't:
update my_table set some_field = JSON_MERGE([1, 2, 3], some_field)
The result of this would be:
id: 1
some_field: [1, 2, 3, 4, 5]
id: 2
some_field: [1, 2, 3, 6, 7]
id: 3
some_field: [1, 2, 3]
Considering you have 3 records in your table and you want to merge 1 and 2 as mentioned in your example.
I hope JavaScript is suitable to follow through for you.
// Get both the records
const records = db.execute(“SELECT id, some_field FROM my_table WHERE id=1 OR id=2”);
// You get both the rows.
// Merging row1, you can either use the Set data structure if you’re dealing with numbers like your example, or you could loop using a map and use the spread operator if using JSON. Since your object is an array, I’ll just be explaining to merge 2 arrays.
records[0].some_field = Array.from(new Set(records[0].some_field + record[1].some_field))
// Same for second record.
records[1].some_field = Array.from(new Set(records[0].some_field + record[1].some_field))
// Now update both the records in the database one by one.
Related
I have a table which has a JSON type field where I save a number array like [1, 2, 3, 4].
I want to select records in which its array set contains at least one element of another array I have in a php script.
I know that the JSON_CONTAINS function can be used to see if my array contains an element, but how can I select if both arrays has at least a common number (no matter in what index).
For example:
[1, 2, 3] and [5, 0, 2] -> True
[9, 2, 1] and [0, 5, 3] -> False
[4, 0, 2] and [4, 2, 6] -> True
Currently, Im using multiple JSON_CONTAINS to check if there are common elements, this way:
SELECT *
FROM mytable
WHERE JSON_CONTAINS(ar, 0, '$') OR
JSON_CONTAINS(ar, 1, '$') OR
JSON_CONTAINS(ar, 2, '$')
But I guess there may be a more elegant way of doing this.
I searched but couldn't find the appropiate function, but if this is a dupe, let me know.
Thanks in advance!
https://dev.mysql.com/doc/refman/8.0/en/json-search-functions.html#function_json-overlaps
mysql> SELECT JSON_OVERLAPS("[1,3,5,7]", "[2,5,7]");
+---------------------------------------+
| JSON_OVERLAPS("[1,3,5,7]", "[2,5,7]") |
+---------------------------------------+
| 1 |
+---------------------------------------+
In PostgreSql I can't find in the docs a function that could allow me to combine n json entities, whilst summing the value part in case of existing key/value pair
English not being my main language, I suspect I don't know how to search with the right terms
In other words
from a table with 2 columns
name data
'didier' {'vinyl': 2, 'cd': 3)
'Anne' {'cd' : 1, 'tape' : 4}
'Pierre' {'cd' : 1, 'tape': 9, 'mp3':2}
I want to produce the following result :
{ 'vinyl' : 2, 'cd' : 5, 'tape':13, mp3 : 2}
With is a "combine and sum" function
Thanks in advance for any idea
Didier
Using the_table CTE for illustration, first 'normalize' data column then sum per item type (k) and finally aggregate into a JSONB object.
with the_table("name", data) as
(
values
('didier', '{"vinyl": 2, "cd": 3}'::jsonb),
('Anne', '{"cd" : 1, "tape" : 4}'),
('Pierre', '{"cd" : 1, "tape": 9, "mp3":2}')
)
select jsonb_object_agg(k, v) from
(
select lat.k, sum((lat.v)::integer) v
from the_table
cross join lateral jsonb_each(data) as lat(k, v)
group by lat.k
) t;
-- {"cd": 5, "mp3": 2, "tape": 13, "vinyl": 2}
I have a json_array [1, 2, 3, 3, 3], and I want to find out where how many the element '3' is.
For example,
json_search('[1, 2, 3, 3, 3]', 'all', 3) return null;
json_search('["1", "2", "3", "3", "3"]', 'all', '3') return ["$[2]", "$[3]", "$[4]"];
Therefore,
json_length(json_search('[1, 2, 3, 3, 3]', 'all', 3)) return null;
I want to 3
I’ve been looking all day, but I don’t know the solution and ask for help.
One option here, assuming you have just a single top level array of JSON integers, would be to use a regex replacement trick to count the number of 3's:
WITH yourTable AS (
SELECT '[1, 2, 3, 3, 3]' AS array
)
SELECT
LENGTH(array) - LENGTH(REGEXP_REPLACE(array, '\\b3\\b', '')) AS num_3
FROM yourTable;
This returns 3 as the length, which is correct.
i have array like this: [1, 1, 1, 2, 3]. How i can get users with a duplicate? For example this query return list without duplicate
list= User.objects.filter(id__in=[1, 1, 1, 2, 3])
for example it will be users with id's:
1,
2,
3
but i need list of users like this:
1,
1,
1,
2,
3
list = []
for x in [1, 1, 1, 2, 3]:
list.append(User.objects.filter(id=x)
It this what you mean? I don't quite understand the spacing.
Get your queryset sorted in the right order. .order_by('id) for ascending by id (which may be the default anyway). Then iterate over the queryset with code to make extra operations with the same object (or a copy thereof) as dictated by the list of IDs.
idlist = [1, 1, 1, 2, 3]
queryset = User.objects.filter(id__in = idlist ).order_by('id')
for object in queryset:
for _ in range( idlist.count( object.id))
do_something_with( object)
Note, this is only one DB call (one queryset), unlike the accepted answer which does one DB query for each element in the id list. Not good.
Sorry for bad English ))
I have an array of ids in my ruby code.
Example:
[[10], [], [10, 1, 3], []]
Can I load User model from MySQL table users in one query by saving grouping?
Example:
[[#<User id=10>], [], [#<User id=10>, #<User id=1>, #<User id=3>], []]
Environment: Ruby 2.5.1 | Rails 5 | MySQL
One of found solution:
I can flat my array of ids and load my model by that array into hash:
hash = User.where(id: array.flatten).index_by(&:id)
Then, during iterating, through array I can load my objects from hash in the right order like that:
array.each do |ids|
users = ids.map { |id| hash[id] }
# do smth
end
This is simple: use flatten method for array:
ids = [[123], [], [123, 1, 3, 4], [70, 80]]
user_ids = ids.flatten.reject(&:blank?).uniq
users = User.where(id: user_ids)
edited:
not optimal (recursive) method for your need:
def map_users_by_id(ids_array:, users:)
result = []
ids_array.each do |array_element|
if (array_element).is_a? Array
result << map_users_by_id(ids_array: array_element, users: users)
else
result << users[array_element]
end
end
return result
end
ids = [[123], [], [123, 1, 3, 4], [70, 80]]
user_ids = ids.flatten.reject(&:blank?).uniq
users = Hash[User.where(id: user_ids).map{|user|[user.id, user]}]
result = map_users_by_id(ids_array: ids, users: users)