I'm having trouble understanding how to write this MySQL query and a lot of the answers I've been able to find here don't seem to help a lot.
I have two tables with these rows:
units
-----------------
unit_id (INT)
unit_name(STRING)
surveys
-----------------
survey_id (INT)
parent_unit(INT)
I am trying to add a record to the surveys table. In my query, I know the unit_name of parent_unit but I need to find out what the unit_id is.
I have not worked with mysql in a while so I am having trouble creating an INNER JOIN that would replace unit_name with the corresponding unit_id.
This is what I have tried so far, but I think I am very far from the answer:
$unit_name = "unit1"
INSERT INTO surveys (parent_unit)
SELECT * FROM units
INNER JOIN units ON $unit_name=units.unit_name
VALUES ("unit name") //This should be an INT
The result of this query would be:
survey_id | parent_unit
----------+------------
0 | 0
As the unid_id for the `parent_unit "unit1" is 0, which we can see in the units table:
> SELECT * FROM units WHERE unit_name LIKE "unit1";
unit_id | unit_name
--------+----------
0 | unit1
I hope I explained myself enough to be understood.
So start simpler. First, what is the query to find a unit id, given the unit name, from units? As an elementary query:
SELECT unit_id
FROM units
WHERE unit_name LIKE "the_unit_name_you_have"
So then we look at what you actually want to do: you need to build a survey record, and you have a unit name. Rather than doing a full table join for every possible unit, let's just repeat that exact select, and just drop that into the table:
INSERT INTO surveys (parent_unit)
SELECT unit_id AS parent_unit
FROM units
WHERE unit_name LIKE "the_unit_name_you_have"
(Also note that that AS is entirely optional, but can make things easier to track as human being)
Based on your explanation seems you need
a join between a 'unit name' from units and a parent_id from sessions based on the relation between unit_id and parent_id
INSERT INTO surveys (parent_unit)
SELECT unit_id
FROM units u
INNER JOIN surveys s ON u.unit_name = 'unit name'
and u.id = s.parent_unit
Related
This question already has answers here:
How to resolve ambiguous column names when retrieving results?
(11 answers)
Closed 2 years ago.
I have some big tables which I need to combine into a single very large table, to form a single-page data export for a statistical package.
This is easy with INNER JOIN but the some of the tables have the same column names and these are being overwritten by each other when I fetch them as an array in PHP.
There are 4 tables being joined with 30-200 columns in each so there are far too many field names to manually include in the query with aliases, as would be the norm in this situation.
Here's the query:
SELECT * FROM logs
INNER JOIN logdetail ON logdetail.logID = logs.id
INNER JOIN clients ON clients.id = logs.clientID
INNER JOIN records ON records.id = logdetail.id
WHERE logs.userID=1
Is there any way around this? I don't actually mind what the column names are as long as I have the data so if I could prepend the table name to each field, that would do the trick.
I would create a view, your view would be comprised of your long query with aliases
Here is an example taken from the manual
mysql> CREATE TABLE t (qty INT, price INT);
mysql> INSERT INTO t VALUES(3, 50);
mysql> CREATE VIEW v AS SELECT qty, price, qty*price AS value FROM t;
mysql> SELECT * FROM v;
+------+-------+-------+
| qty | price | value |
+------+-------+-------+
| 3 | 50 | 150 |
+------+-------+-------+
This has always worked for me, unless you have one to many or some other relationship among these tables, which will duplicate records.
SELECT * FROM logs l
INNER JOIN logdetail ld ON ld.logID = l.id
INNER JOIN clients c ON c.id = l.clientID
INNER JOIN records r ON r.id = ld.id
WHERE l.userID=1
As andrew says you can also use a View to get this thing working which is much cooler.
I found a solution for this. Simply, fetch each duplicate column a second time, this time using an alias. This way, the overwritten values are selected again and aliased:
SELECT * FROM logs,
clients.name as clientName,
logs.name as logName,
etc...
INNER JOIN logdetail ON logdetail.logID = logs.id
INNER JOIN clients ON clients.id = logs.clientID
INNER JOIN records ON records.id = logdetail.id
WHERE logs.userID=1
Note: There is no need to do this for the final instance of the duplicate, because this column will not have been overwritten. So, in the example above, there is no need to include a line like records.name as recordName because, since there are no columns after it which have the same name, the record.name field was never overwritten and is already available in the name column.
I have a series of tables that I want to get rows returned from in the following format:
Student ID | Last Name | First Name | Quiz Scores
-------------------------------------------------
xxxxxxx | Snow | Jon | 0,0,0,0,0,0,0,0
There's 3 relevant tables (changing any existing DB structure is not an option):
person - table of all people in the organization
enrollment - table of student and faculty enrollment data
tilt.quiz - table of quiz scores, with each row storing an individual score
The tricky part of this is the Quiz Scores. A row for the quiz score only exists if the student has taken a the quiz. Each quiz row has a module, 1 - 8. So possible quiz data for a student could be (each of these being a separate row):
person_id | module | score
---------------------------
223355 | 1 | 100
223355 | 2 | 95
223355 | 4 | 80
223355 | 7 | 100
I need the quiz scores returned in proper order with 8 comma separated values, regardless if any or all of the quizzes are missing.
I currently have the following query:
SELECT
person.id,
first_name,
last_name,
GROUP_CONCAT(tilt.quiz.score) AS scores
FROM person
LEFT JOIN enrollment ON person.id = enrollment.person_id
LEFT JOIN tilt.quiz ON person.id = tilt.quiz.person_id
WHERE
enrollment.course_id = '$num' AND enrollment_status_id = 1
GROUP BY person.id
ORDER BY last_name
The problems with this are:
It does not order the quizzes by module
If any of the quizzes are missing it simply returns fewer values
So I need the GROUP_CONCAT scores to at least include commas for missing quiz values, and have them ordered correctly.
The one solution I considered was creating a temporary table of the quiz scores, but I'm not sure this is the most efficient method or exactly how to go about it.
EDIT: Another solution would be to execute a query to check for the existence of each quiz individually but this seems clunky (a total of 9 queries instead of 1); I was hoping there was a more elegant way.
How would this be accomplished?
There are some assumptions here about your data structure, but this should be pretty close to what you're after. Take a look at the documentation for GROUP_CONCAT and COALESCE.
SELECT `person`.`id`, `person`.`first_name`, `person`.`last_name`,
GROUP_CONCAT(
COALESCE(`tilt`.`quiz`.`score`, 'N/A')
ORDER BY `tilt`.`quiz`.`module_id`
) AS `scores`
FROM `person`
CROSS JOIN `modules`
LEFT JOIN `enrollment` USING (`person_id`)
LEFT JOIN `tilt`.`quiz` USING (`person_id`, `module_id`)
WHERE (`enrollment`.`course_id` = '$num')
AND (`enrollment`.`enrollment_status_id` = 1)
GROUP BY `person`.`id`
ORDER BY `person`.`last_name`
First thing to do is use the IFNULL() function on the score
Then, use ORDER BY inside the GROUP_CONCAT
Here is my proposed query
SELECT
person.id,
first_name,
last_name,
GROUP_CONCAT(IFNULL(tilt.quiz.score,0) ORDER BY tilt.quiz.module) AS scores
FROM person
LEFT JOIN enrollment ON person.id = enrollment.person_id
LEFT JOIN tilt.quiz ON person.id = tilt.quiz.person_id
WHERE
enrollment.course_id = '$num' AND enrollment_status_id = 1
GROUP BY person.id
ORDER BY last_name
So, I have a table named clients, another one known as orders and other two, orders_type_a and orders_type_b.
What I'm trying to do is create a query that returns the list of all clients, and for each client it must return the number of orders based on this client's id and the amount of money this customer already spent.
And... I have no idea how to do that. I know the logic behind this, but can't find out how to translate it into a MySQL query.
I have a basic-to-thinkimgoodbutimnot knowledge of MySQL, but to this situation I've got really confused.
Here is a image to illustrate better the process I'm trying to do:
Useful extra information:
Each orders row have only one type (which is A or B)
Each orders row can have multiple orders_type_X (where X is A or B)
orders relate with client through the column client_id
orders_type_X relate with orders through the column order_id
This process is being made today by doing a query to retrieve clients, and then from each entry returned the code do another query (with php) to retrieve the orders and yet another one to retrieve the values. So basically for each row returned from the first query there is two others inside it. Needless to say that this is a horrible approach, the performance sucks and I thats the reason why I want to change it.
UPDATE width tables columns:
clients:
id | name | phone
orders:
id | client_id | date
orders_type_a:
id | order_id | number_of_items | price_of_single_item
orders_type_b:
id | order_id | number_of_shoes_11 | number_of_shoes_12 | number_of_shoes_13 | price_of_single_shoe
For any extra info needed, just ask.
If I understand you correctly, you are looking for something like this?
select c.*, SUM(oa.value) + SUM(ob.value) as total
from clients c
inner join orders o on c.order_id = o.id
inner join orders_type_a oa on oa.id = o.order_type_id AND o.type = 'A'
inner join orders_type_b ob on ob.id = o.order_type_id AND o.type = 'B'
group by c.id
I do not know your actual field names, but this returns the information on each customer plus a single field 'total' that contains the sum of the values of all the orders of both type A and type B. You might have to tweak the various names to get it to work, but does this get you in the right direction?
Erik's answer is on the right track. However, since there could be multiple orders_type_a and orders_type_b records for each order, it is a little more complex:
SELECT c.id, c.name, c.phone, SUM(x.total) as total
FROM clients c
INNER JOIN orders o
ON o.client_id = c.id
INNER JOIN (
SELECT order_id, SUM(number_of_items * price_of_single_item) as total
FROM orders_type_a
UNION ALL
SELECT order_id, SUM((number_of_shoes_11 + number_of_shoes_12 + number_of_shoes_13) * price_of_single_shoe) as total
FROM orders_type_b
) x
ON x.order_id = o.id
GROUP BY c.id
;
I'm making a few assumptions about how to calculate the total based on the columns in the orders_type_x tables.
I have two tables, one called episodes, and one called score. The episode table has the following columns:
id | number | title | description | type
The score table has the following columns:
id | userId | showId | score
The idea is that users will rate a show. Each time a user rates a show, a new row is created in the score table (or updated if it exists already). When I list the shows, I average all the scores for that show ID and display it next to the show name.
What I need to be able to do is sort the shows based on their average rating. I've looked at joining the tables, but haven't really figured it out.
Thanks
To order the results, use and ORDER BY clause. You can order by generated columns, such as the result of an aggregate function like AVG.
SELECT e.title, AVG(s.score) AS avg_score
FROM episodes AS e
LEFT JOIN scores AS s ON e.id=s.showId
GROUP BY e.id
ORDER BY avg_score DESC;
You're right. You have to JOIN these tables, then use GROUP BY on the 'episodes' table's 'id' column. Then you'll be able to use AVG() function on 'the scores' tables's 'score' column.
SELECT AVG(scores.score) FROM episodes LEFT JOIN scores ON scores.showId = episodes.id GROUP BY episodes.id
SELECT episodes.*, AVG(score.score) as AverageRating FROM episodes
INNER JOIN score ON (episodes.id = score.showId)
GROUP BY episodes.id
ORDER BY AVG(score.score) DESC
Hi guys I have the following three tables here.
COUNTRIES
ID | Name | Details
Airports
ID | NAME | CountryID
Trips
ID | AirportID | Date
I have to retrieve a list showing the following:
AirportID | AIrport Name | Country Name | Number of Trips Made Between Date1 and Date2
I need this to be really efficient, what kind of indexes do I need to set up and how would I formulate the SQL query here? I would be displaying this using Php. Note that I need to be able to sort based upon the number of trips made.
EDIT ==
Oops forgot to mention my sql:
I've tried the following:
SELECT `c`.*, `t`.`country` AS `country_name`, COUNT(f.`id`) AS `num_trips` FROM `airports` AS `c`
LEFT JOIN `countries` AS `t` ON t.`id` = c.`country_id`
LEFT JOIN `trips` AS `f` ON f.`airportid` = c.`id` GROUP BY `c`.`id` ORDER BY `num_flights` ASC LIMIT 10
It works but takes a really looong time to execute - plus consider this that my airports table has over 30'000 entries and teh trips table is variable.
I'm just taking the name of the country from the countries table - would it be better if I were to instead exclude joining teh countries table in the sql and instead retrieve the country name from an array where the index is the ID and values are the names of countries?
I'm not sure why you're using left joins. If every trip has an airport and every airport has a country, and inner join would give you accurate results.
I would do this:
select a.ID as AirportID, a.Name as AirportName, c.Name as CountryName, count(t.id) as NumTrips
from Trips t
inner join Airports a on t.AirportID = a.ID
inner join Countries c on a.CountryID = c.ID
where t.Date >= #StartDate
and t.Date <= #EndDate
group by AirportID, AirportName, CountryName
order by NumTrips
limit 10
Replace the #StartDate and #EndDate with your appropriate values.
Not sure what you're looking for in results, but I would expect you want the most trips. In that case you would want to do "order by NumTrips desc". This will show the highest values first, especially since you're limiting it to 10.
Also, I suggest you rename your "Date" column to something that won't collide with reserved SQL words. I usually use "DateCreated" or "DateOfTravel" or something like that.
If I made any poor assumptions let me know and I can re-write this.
Edit:
For indexes, create them on fields you will be looking up on. In other words, primary keys (which should always be indexed), foreign keys, and in this case it looks like the Date column would be the other important index. However, if you plan on searching by "Airport Name", then add an index there. I think you see where this is headed, etc.
Indexes on airpoirt(countryid, id) and trips(airportid) would seem the most important.
Instead of count(f.id) try count(f.airportid), so MySQL doesn't have to check the trips.id column.