I use Sequelize ORM for Node.js. I need to get lines with unique values in certain column. Example table:
id | name | group
-----------------
1 | One | 2
2 | Two | 1
3 | Three| 2
4 | Four | 3
5 | Five | 1
Query for column group and result:
id | name | group
-----------------
1 | One | 2
2 | Two | 1
4 | Four | 3
Lines One, Two and Four was the first who had unique group values. How to make it in Sequelize?
A Sequelize raw query is one way of getting out the rows that you want:
/*
var sql =
SELECT r.id,
r.name,
r.groupnum
FROM s04.row r
JOIN
(SELECT min(id) AS id,
groupnum
FROM s04.row
GROUP BY groupnum) s
ON r.id = s.id
*/
return sq.query(sql, { type: sq.QueryTypes.SELECT});
The resulting promise will resolve to a JSON array:
[
{
"id": 1,
"name": "One",
"groupnum": 2
}
...
]
If you then needed to work with these rows as Instances you can call build on each element of the array:
Model.build({ /* attributes-hash */ }, { isNewRecord: false })
See here for an example. If I find a way of doing this via Sequelize function calls (aggregate, find*, etc) that isn't too hideous I'll also post that here as a separate answer.
Related
I want to be able to filter out groups where the values aren't the same. When doing the query:
SELECT
category.id as category_id,
object.id as object_id,
object.value as value
FROM
category,
object
WHERE
category.id = object.category
We get the following results:
category_id | object_id | value
-------------+-----------+-------
1 | 1 | 1
1 | 2 | 2
1 | 3 | 2
2 | 4 | 3
2 | 5 | 2
3 | 6 | 1
3 | 7 | 1
The goal: Update the query so that it yields:
category_id
-------------
1
2
In other words, find the categories where the values are different from the others in that same category.
I have tried many different methods of joining, grouping and so on, to no avail.
I know it can be done with multiple queries and then filter with a little bit of logic, but this is not the goal.
You can use aggregation:
SELECT o.category as category_id
FROM object o
GROUP BY o.category
HAVING MIN(o.value) <> MAX(o.value);
You have left the FROM clause out of your query. But as written, you don't need a JOIN at all. The object table is sufficient -- because you are only fetching the category id.
Hello guys please bear with me here. I'm using PostgreSQL, Sequelize, Express, and NodeJS to create a backend. I'm wondering if these lines of raw query code can be implemented using Sequelize Model findAll function.
First of all, what I am trying to do here is to calculate the total score of these students. Here are some tables and their relations.
Student Level
| student_id | name | level_id | | level_id | level_name |
|:----------:|:----------:|:--------:| |:--------:|:----------:|
| 1 | John | 1 | > | 1 | Rookie |
| 2 | Jane | 2 | | 2 | Expert |
v
StudentQuiz
| quiz_id | student_id | score |
|:----------:|:----------:|:--------:|
| 1 | 1 | 40 |
| 1 | 1 | 100 |
| 2 | 1 | 80 |
| 1 | 2 | 100 |
| 2 | 2 | 100 |
If I run line of codes below.
SELECT table2.student_id,
s.canvasser_name,
l.level_name,
table2.total_score
FROM (SELECT table1.student_id,
sum(table1.max_score) total_score
FROM (SELECT sq.student_id,
max(sq.score) max_score
FROM public.StudentQuiz sq
GROUP BY sq.quiz_id, sq.student_id) table1
GROUP BY table1.student_id) table2
INNER JOIN public.Student s
ON s.student_id = table2.student_id
INNER JOIN public.Level l
ON l.level_id = s.level_id
ORDER BY table2.total_score DESC
LIMIT 10;
I will get something like this.
| student_id | name | level | total_score |
|:----------:|:----------:|:--------:|:--------------:|
| 1 | John | Rookie | 180 |
| 2 | Jane | Expert | 200 |
Please note that I'm selecting the highest score if more than one quiz with the same id found.
Anyway, I want to implement it using sequelize built in function. What I've been trying to do is something like this.
const result = await StudentQuiz.findAll({
attributes: ['studentId', [sequelize.fn('sum', sequelize.fn('max', sequelize.col('score'))), 'totalPrice'], 'quizId'],
group: 'studentId',
include: [
{
model: Student,
include: [{
model: Level
}],
},
],
offset: 0,
limit: 10
});
The code above throws an error message which is "aggregate function calls cannot be nested".
Any kind of help will be appreciated. Thank you.
P.S. I know i can use sequelize.query() function to use the first code block shown, but that's not the point.
Sequelize is not intended to work with complex aggregations using models. Its primary goal is to provide CRUD operations with models.
To use models in such scenario you can use a model definition to get a schema, a table name and fields to build a query dynamically not knowing exact field names.
I find the solution without using any raw query, though I need to get two tables, that is StudentQuiz and Student that coupled by Level. Here is my answer.
// Finding maximum score and group it based on studentId and quizId
const maxScoreList = await StudentQuiz.findAll({
attributes: ['studentId', 'quizId', [sequelize.fn('max', sequelize.col('score')), 'maxScore']],
group: ['studentId', 'quizId'],
order: ['studentId', 'quizId'],
raw: true
});
// Calculating total score for the same student for each quiz recorded
const scoreArray = [maxScoreList.shift()];
let index = 0;
const unfilteredStudentId = maxScoreList.map((item) => {
if (scoreArray[index].studentId !== item.studentId) {
scoreArray.push(item);
index += 1;
}
scoreArray[index].maxScore += item.maxScore;
return item.studentId;
});
// Filtering studentId that show up more than one time
const extractedStudentId = [...new Set(unfilteredStudentId)];
// Finding student based on studentId inside extractedStudentId array
const student = await Student.findAll({
where: { id: extractedStudentId },
attributes: ['id', 'canvasserId', 'canvasserName', 'canvasserImageUrl'],
include: {
model: Level,
attributes: [['level_name', 'level'], ['icon_url', 'level_image_url']]
},
order: ['id'],
raw: true,
nest: true
});
// Combining total score list to student list
const rankList = student.map((item, idx) => ({ ...item, totalScore: scoreArray[idx] }));
With this much complexity, I agree that using raw query by far the best approach for this case.
I have a table called diary which includes columns listed below:
| id | user_id | custom_foods |
|----|---------|--------------------|
| 1 | 1 | {"56": 2, "42": 0} |
| 2 | 1 | {"19861": 1} |
| 3 | 2 | {} |
| 4 | 3 | {"331": 0} |
I would like to count how many diaries having custom_foods value(s) larger than 0 each user have. I don't care about the keys, since the keys can be any number in string.
The desired output is:
| user_id | count |
|---------|---------|
| 1 | 2 |
| 2 | 0 |
| 3 | 0 |
I started with:
select *
from diary as d
join json_each_text(d.custom_foods) as e
on d.custom_foods != '{}'
where e.value > 0
I don't even know whether the syntax is correct. Now I am getting the error:
ERROR: function json_each_text(text) does not exist
LINE 3: join json_each_text(d.custom_foods) as e
HINT: No function matches the given name and argument types. You might need to add explicit type casts.
My using version is: psql (10.5 (Ubuntu 10.5-1.pgdg14.04+1), server 9.4.19). According to PostgreSQL 9.4.19 Documentation, that function should exist. I am so confused that I don't know how to proceed now.
Threads that I referred to:
Postgres and jsonb - search value at any key
Query postgres jsonb by value regardless of keys
Your custom_foods column is defined as text, so you should cast it to json before applying json_each_text. As json_each_text by default does not consider empty jsons, you may get the count as 0 for empty jsons from a separate CTE and do a UNION ALL
WITH empty AS
( SELECT DISTINCT user_id,
0 AS COUNT
FROM diary
WHERE custom_foods = '{}' )
SELECT user_id,
count(CASE
WHEN VALUE::int > 0 THEN 1
END)
FROM diary d,
json_each_text(d.custom_foods::JSON)
GROUP BY user_id
UNION ALL
SELECT *
FROM empty
ORDER BY user_id;
Demo
I have a question concerning MS Access queries involving these tables:
tblMIDProcessMain ={ Process_ID,Process_Title,...}
tblMIDProcessVersion = { ProcessVersion_ID, ProcessVersion_FK_Process, ProcessVersion_VersionNo, ProcessVersion_FK_Status, ...}
tblMIDProcessVersionStatus = { ProcessVersionStatus_ID,ProcessVersionStatus_Value }
The tables store different versions of a process description. The "ProcessVersion_VersionNo" field contains an integer providing the version number. Now I would like to get for each process the highest version number thus the current version. If I do the following it kind of works:
SELECT tblMIDProcessMain.Process_Titel
, Max(tblMIDProcessVersion.ProcessVersion_VersionNo) AS CurrentVersion
FROM tblMIDProcessMain
INNER JOIN tblMIDProcessVersion
ON tblMIDProcessMain.Process_ID = tblMIDProcessVersion.ProcessVersion_FK_Process
GROUP BY tblMIDProcessMain.Process_Titel;
The query returns a recordset with each existing process_title and the respective max number of the version field. But as soon as I add other fields like "ProcessVersion_FK_Status" in the Select statement the query stops working.
Any help would be appreciated. Thanks in advance.
Jon
Edit:
To clarify things a little I added a simplified example
Parent-Table:
Process_ID | Process_Title
----------------------------------
1 | "MyProcess"
2 | "YourProcess"
Child-Table:
Version_ID | Version_FK_ProcessID | Version_No | Version_Status
---------------------------------------------------------------------------
1 | 1 | 1 | "New"
2 | 2 | 1 | "Discarded"
3 | 2 | 2 | "Reviewed"
4 | 2 | 3 | "Released"
Intended Result:
Title | Max_Version_No | Status
--------------------------------------------------------
MyProcess | 1 | "New"
YourProcess | 3 | "Released"
Given the example tables you updated your post with, this should work:
select process_title as Title
, max_version.max_version_no
, c.version_status as status
from (parenttable p
inner join (select max(version_id) as max_version_no, version_fk_process_id from childtable group by version_fk_process_id) max_version
on p.process_id = max_version.version_fk_process_id)
inner join childtable c
on max_version.max_version_no = c.version_id and max_version.version_fk_process_id = c.version_fk_process_id
I assume you are adding the new field to the 'Group By" clause? If not, then you either must include in the 'Group By', or you must use one of the operators like "Max" or "First" etc.
i have a table like this one:
--------------------------------
id | name
--------------------------------
1 | aa
2 | aa
3 | aa
4 | aa
5 | bb
6 | bb
... one million more ...
and i like to obtain an arbitrary number of rows in a pre defined sequence and the other rows ordered by their name. e.g. in another table i have a short sequence with 3 id's:
sequ_no | id | pos
-----------------------
1 | 3 | 0
1 | 1 | 1
1 | 2 | 2
2 | 65535 | 0
2 | 45 | 1
... one million more ...
sequence 1 defines the following series of id's: [ 3, 1, 2]. how to obtain the three rows of the first table in this order and the rest of the rows ordered by their name asc?
how in PostgreSQL and how in mySQL? how would a solution look like in hql (hibernate query language)?
an idea i have is to first query and sort the rows which are defined in the sequence and than concat the other rows which are not in the sequence. but this involves tow queries, can it be done with one?
Update: The final result for the sample sequence [ 3, 1, 2](as defined above) should look like this:
id | name
----------------------------------
3 | aa
1 | aa
2 | aa
4 | aa
5 | bb
6 | bb
... one million more ...
i need this query to create a pagination through a product table where part of the squence of products is a defined sequence and the rest of the products will be ordered by a clause i dont know yet.
I'm not sure I understand the exact requirement, but won't this work:
SELECT ids.id, ids.name
FROM ids_table ids LEFT OUTER JOIN sequences_table seq
WHERE ids.id = seq.id
ORDER BY seq.sequ_no, seq.pos, ids.name, ids.id
One way: assign a position (e.g. 0) to each id that doesn't have a position yet, UNION the result with the second table, join the result with the first table, and ORDER BY seq_no, pos, name.