I have following DB structure:
Table cars:
+----+-----------------------+
| id | few other columns.... |
+----+-----------------------+
| 1 | ... |
| 2 | ... |
| 3 | ... |
+----+-----------------------+
Table properties:
+----+-------+
| id | name |
+----+-------+
| 1 | title |
| 2 | type |
| 3 | brand |
| 4 | color |
+----+-------+
Table cars_properties:
+----+--------+-------------+------------+
| id | car_id | property_id | txt |
+----+--------+-------------+------------+
| 1 | 1 | 1 | Volvo V70 |
| 2 | 1 | 2 | personal |
| 3 | 1 | 3 | Volvo |
| 4 | 1 | 4 | white |
| 5 | 2 | 1 | Volvo VV |
| 6 | 2 | 2 | personal |
| 7 | 2 | 3 | Volvo |
| 8 | 2 | 4 | blue |
| 9 | 3 | 1 | Volvo XXL |
| 10 | 3 | 2 | truck |
| 11 | 3 | 3 | Volvo |
| 12 | 3 | 4 | white |
+----+--------+-------------+------------+
I would like to get all cars that have unique/duplicated values in one or many properties. Currently I'm using this SQL pattern to get duplicates for car type and brand:
SELECT cars.id FROM cars
LEFT JOIN cars_properties AS cp_0 ON cp_0.car_id = cars.id AND cp_0.property_id = 2 # => type
LEFT JOIN cars_properties AS cp_1 ON cp_1.car_id = cars.id AND cp_1.property_id = 3 # => brand
INNER JOIN (
SELECT cp_0.txt AS type_txt, cp_1.txt AS brand_txt FROM cars
LEFT JOIN cars_properties AS cp_0 ON cp_0.car_id = cars.id AND cp_0.property_id = 2
LEFT JOIN cars_properties AS cp_1 ON cp_1.car_id = cars.id AND cp_1.property_id = 3
GROUP BY cp_0.txt, cp_1.txt
HAVING COUNT(cars.id) > 1
) dupes ON cp_0.txt=dupes.type_txt AND cp_1.txt=dupes.brand_txt;
And expected result is:
+----+
| id |
+----+
| 1 |
| 2 |
+----+
Explanation: Both cars with id = 1 and 2 has type and brand that is present in more than one car (multiple times).
As for unique cars, I'm just altering: HAVING COUNT(cars.id) = 1 and I want to find all rows where the combination of properties is present only in one car (once).
It works fine, but it's extremely slow with more than 2 properties I want to check.
I cannot change the DB structure, and I'm not sure how to optimize the query, or if there are better ways of achieving this.
It feels like I would need to implement counter table, where each property id and value (txt) would also store corresponding number of occurrences in cars, and update this counter on every insert/update/delete... But I still hope there is some better SQL, that could help. Do you know some? Any advice greatly appreciated, thanks!
PS: I tried to create fiddle for it, but after I build schema I cannot run any SQL on it. To quickly setup DB with data, you can check SQL Fiddle
Related
As written on the title, does CROSS JOIN not work for different tables with the same column name?
For example,
I have one table named Fruits:
| name | price |
| apple | 1 |
| banana | 2 |
and another table named Snacks:
| name | price |
| chips | 3 |
| cookies | 4 |
Then does
SELECT Fruits.price, Snacks.price FROM Fruits CROSS JOIN Snacks
does not work properly?
I am working on a same issue, but the result shows like:
| price | price |
| 3 | 3 |
| 4 | 4 |
| 3 | 3 |
| 4 | 4 |
But what I expect is:
| price | price |
| 1 | 3 |
| 1 | 4 |
| 2 | 3 |
| 2 | 4 |
As I mentioned in the comment, it is not possible. Either your tables values are different or your query.
Check this dbfiddle showing the result value same as your expected values.
In MySQL CROSS JOIN works as expected:
price price
------ -----
1 3
2 3
1 4
2 4
See running example at DB Fiddle.
I need a help with mySQL SELECT query from multiple tables. I have got four tables: school, discipline, pupils and teams.
School table looks like:
+------+---------+---------------+----------+
| id | name | discipline_id | pupil_id |
+------+---------+---------------+----------+
| 1 | one | 2 | 5 |
+------+---------+---------------+----------+
| 2 | two | 3 | 8 |
+------+---------+---------------+----------+
| 3 | three | 4 | 12 |
+------+---------+---------------+----------+
Discipline table looks like:
+------+---------+
| id | name |
+------+---------+
| 1 | math |
+------+---------+
| 2 | bio |
+------+---------+
| 3 | liter |
+------+---------+
| 4 | geo |
+------+---------+
Teams table looks like:
+------+---------+---------------+-----------+
| id | name | school_id | member_id |
+------+---------+---------------+-----------+
| 1 | T1 | 1 | 3 |
+------+---------+---------------+-----------+
| 2 | T2 | 3 | 3 |
+------+---------+---------------+-----------+
| 3 | T3 | 2 | 9 |
+------+---------+---------------+-----------+
The result of disciplines I need to get with a "SELECT from discipline..." query by "member_id = 3" is:
+-----------------+---------------+
| discipline_name | discipline_id |
+-----------------+---------------+
| bio | 2 |
+-----------------+---------------+
| geo | 4 |
+-----------------+---------------+
By matching member's school and then getting its discipline, if it makes sense...Is it possible to do with just one mySQL query?
Type of: member_id 3 => school_id 1,3 => discipline_id = show related disciplines names and ids which are 2, 4
Thank you very much...
Your goal is not clear or makes no sense to me.
But here is what you are literally asking for:
SELECT
s.discipline_id
d.name
FROM teams t
LEFT JOIN school s
ON s.id = t.school_id
LEFT JOIN discipline d
ON d.id = s.discipline_id
WHERE t.member_id = 3
this is my first time posting here. I don't seem to find the answer to my problem.
So... I'm arranging a DB for a school project, a cookbook that only shows recipes that can be made with existing elements from the "shelf".
These ingredients have to have an exact ingredients match.
user:
+---------------+------+----------+----------+
| email | name | lastname | password |
+---------------+------+----------+----------+
| pal#mail.com | John | Potato | password |
| they#mail.com | Mary | Carrot | password |
+---------------+------+----------+----------+
shelf:
+---------+------------+---------------+
| shelfID | ingredient | user |
+---------+------------+---------------+
| 1 | 1 | pal#mail.com |
| 2 | 2 | pal#mail.com |
| 3 | 3 | pal#mail.com |
| 4 | 4 | pal#mail.com |
| 5 | 10 | they#mail.com |
| 6 | 12 | they#mail.com |
+---------+------------+---------------+
This is my recipe_ingredient relationship table
recipe_ingredient:
+--------+------------+
| recipe | ingredient |
+--------+------------+
| 1 | 1 |
| 1 | 2 |
| 1 | 4 |
| 1 | 10 |
| 2 | 1 |
| 2 | 2 |
| 2 | 3 |
| 2 | 4 |
| 3 | 2 |
| 3 | 3 |
| 3 | 15 |
+--------+------------+
I've tried this query:
SELECT
rec_ing.recipe, shf.ingredient, shf.user
FROM
recipes_ingredients AS rec_ing
INNER JOIN
shelf AS shf ON rec_ing.ingredient = shf.ingredient
INNER JOIN
users AS usr ON shf.user = usr.email
WHERE
usr.email = 'pal#mail.com'
that returns this table:
+--------+------------+--------------+
| recipe | ingredient | user |
+--------+------------+--------------+
| 1 | 1 | pal#mail.com |
| 1 | 2 | pal#mail.com |
| 1 | 4 | pal#mail.com |
| 2 | 1 | pal#mail.com |
| 2 | 2 | pal#mail.com |
| 2 | 3 | pal#mail.com |
| 2 | 4 | pal#mail.com |
| 3 | 2 | pal#mail.com |
| 3 | 3 | pal#mail.com |
+--------+------------+--------------+
Although it's true that the Recipe 1 contains ingredients from my shelf, it's also missing Ingredient 10
+--------+------------+
| recipe | ingredient |
+--------+------------+
| 1 | 1 |
| 1 | 2 |
| 1 | 4 |
| 1 | 10 |
| ... | ... |
+--------+------------+
I'm trying to only get this kind of result set.
+--------+------------+
| recipe | ingredient |
+--------+------------+
| 2 | 1 |
| 2 | 2 |
| 2 | 3 |
| 2 | 4 |
+--------+------------+
Because Recipe 2 contains all elements from my shelf
I have been going around all day with this problem ... What could be missing?
This is a bit tricky, because you need to aggregate your current query by recipe, but you also need the original query to get back the full records. Sadly, MySQL does not support common table exprrssions or other features which could give us a less verbose query.
SELECT
rec_ing.recipe,
shf.ingredient,
shf.user
FROM recipes_ingredients AS rec_ing
INNER JOIN shelf AS shf
ON rec_ing.ingredient = shf.ingredient
INNER JOIN users AS usr
ON shf.user = usr.email
INNER JOIN
(
SELECT rec_ing.recipe
FROM recipes_ingredients AS rec_ing
INNER JOIN shelf AS shf
ON rec_ing.ingredient = shf.ingredient
LEFT JOIN users AS usr
ON shf.user = usr.email
WHERE
usr.email = 'pal#mail.com'
GROUP BY rec_ing.recipe
HAVING COUNT(usr.email) = COUNT(*)
) t
ON rec_ing.recipe = t.recipe
WHERE
usr.email = 'pal#mail.com'
The basic strategy here is to just do one additional join to a subquery which identifies all recipes where every ingredient belongs to a given user. The critical part is the following:
HAVING COUNT(usr.email) = COUNT(*)
This checks that the total number of rows for a given recipe matches the number of rows which have been assigned to a given user.
I would like to calculate average from nested relationship between eloquent models. So, let's say, I have 3 tables called programs, activities and statistics.
For simplicity sake, I will try to minimize the structure as follows:
program table:
-------------
| id | name |
-------------
| 1 | Foo |
| 2 | Bar |
-------------
activities table:
-----------------------------------
| id | program_id | name |
-----------------------------------
| 1 | 1 | Foo 1 |
| 2 | 1 | Foo 2 |
| 3 | 1 | Foo 3 |
| 4 | 2 | Bar 1 |
| 5 | 2 | Bar 2 |
-----------------------------------
statistics table:
-----------------------------------
| id | activity_id | type | score |
-----------------------------------
| 1 | 1 | A | 25 |
| 2 | 1 | B | 20 |
| 3 | 1 | A | 22 |
| 4 | 2 | A | 27 |
| 5 | 2 | B | 24 |
| 6 | 3 | A | 23 |
-----------------------------------
Now, what I want to get is the average of score of a program with specific type of statistic. I defined relationship in models, and tried following code, but no avail:
$program = Program::find(1);
$avg = $program->activities->where('statistics.type', 'A')->avg('statistics.value');
$avg always 0 or null if there is no activities in program, even without where clause.
i'm sure that i defined the relationship correctly because $program->activities returns a sets of activities and $activity-> statistics return a sets of statistics as well.
Any ideas?
You can use whereHas() like this:
Statistics::whereHas('activity', function ($q) use($programId) {
$q->where('program_id', $programId);
})
->where('type', 'A')
->avg('score');
Make sure you've defined activity relationship which should be "statistics belongsTo() activity".
I have a table that looks like this:
+----+--------+-------+
| id | entity | word |
+----+--------+-------+
| 1 | 1 | red |
| 2 | 1 | green |
| 3 | 1 | blue |
| 4 | 2 | car |
| 5 | 2 | truck |
| 6 | 2 | train |
| 7 | 3 | water |
| 8 | 3 | milk |
| 9 | 3 | soda |
+----+--------+-------+
If I do a search for blue I would like to get red, green and blue as an answer. Right now I am using 2 queries. One to find the 'entity' number and one to find all the words with the same 'entity' number.
Try this. Join is much faster than subquery
select distinct t2.word from Table t1
INNER JOIN Table t2 on t2.entity=t1.entity
where t1.word="blue";
SELECT *
FROM TABLE_NAME
WHERE entity IN
(SELECT entity
FROM TABLE_NAME
WHERE word='blue');