This is a simple query problem. But it seems that I can't get it right :(
I just started using cakephp last week. I'm still playing around exploring. Anyway, here's my problem.
This is the relationship in Model: Product has many Stock. Stock belongs to Product.
This is the sample STOCKS table:
ID | Product Name | Transaction
------------------------------------
1 | Astringent | Purchase
2 | Glutathione | Sales
3 | Glutathione | Sales
I would like to get the number of transaction per product from the STOCKS table.
This is the output I would like with distinct product name:
Transaction | Astringent | Glutathione
--------------------------------------------
purchase | 1 | 0
sales | 0 | 2
Here is a sql query- for exactly what you requested.
SELECT transaction,
SUM(
CASE
WHEN product_name = 'Astringent' THEN 1
ELSE 0
END) AS 'Astringent',
SUM(
CASE
WHEN product_name = 'Glutathione' THEN 1
ELSE 0
END) AS 'Glutathione'
FROM stock
GROUP BY transaction;
However, are you looking for a pivot table i.e., an output with a variable number of columns based on a random number of products? If so, your solution is lot more complicated as a MySQL query, and potentially less complicated as a MySQL and PHP solution. In either case, I think you should share more of your database schema / CakePHP model along with some controller information. In order to render a view with this table is not overly difficult as long as you want Cakephp to output this format.
Related
I have tables in which are banking operations and other tables with the amount of operations.
Operation Id | name operation
-------------+----------------
0 | transfer
1 | registration
2 | BLIK
Operation Id | amount
-------------+--------
0 | 15,000
1 | 53,000
2 | 200
E.t.c
I was supposed to write a query that shows the names of the operations in the form of a column together with the amount. Well, I wrote something like this:
Select
case id_operacji
when 0 then amount
end as 'transfer',
case id_operacji
when 1 then amount
end as 'registration ',
case operation id
when 2 then amount of operation
end as 'BLIK'
from ...
In response to the above solution I received information that the main problem is to check that the header will depend on the change of the operation name. Could someone help me how to do it?
As far as I can tell, you are looking for JOIN between the two tables:
select a.amount, o.name_operation
from operations o
join amounts a on o.operation_id = a.operation_id;
I had to guess the table and column names as you did not disclose the real table structures.
I take a Database course in which we have listings of AirBnBs and need to be able to do some SQL queries in the Relationship-Model we made from the data, but I struggle with one in particular :
I have two tables that we are interested in, Billing and Amenities. The first one have the id and price of listings, the second have id and wifi (let's say, to simplify, that it equals 1 if there is Wifi, 0 otherwise). Both have other attributes that we don't really care about here.
So the query is, "What is the difference in the average price of listings with and without Wifi ?"
My idea was to build to JOIN-tables, one with listings that have wifi, the other without, and compare them easily :
SELECT avg(B.price - A.price) as averagePrice
FROM (
SELECT Billing.price, Billing.id
FROM Billing
INNER JOIN Amenities
ON Billing.id = Amenities.id
WHERE Amenities.wifi = 0
) A, (
SELECT Billing.price, Billing.id
FROM Billing
INNER JOIN Amenities
ON Billing.id = Amenities.id
WHERE Amenities.wifi = 1) B
WHERE A.id = B.id;
Obviously this doesn't work... I am pretty sure that there is a far easier solution to it tho, what do I miss ?
(And by the way, is there a way to compute the absolute between the difference of price ?)
I hope that I was clear enough, thank you for your time !
Edit : As mentionned in the comments, forgot to say that, but both tables have idas their primary key, so that there is one row per listing.
Just use conditional aggregation:
SELECT AVG(CASE WHEN a.wifi = 0 THEN b.price END) as avg_no_wifi,
AVG(CASE WHEN a.wifi = 1 THEN b.price END) as avg_wifi
FROM Billing b JOIN
Amenities a
ON b.id = a.id
WHERE a.wifi IN (0, 1);
You can use a - if you want the difference instead of the specific values.
Let's assume we're working with data like the following (problems with your data model are noted below):
Billing
+------------+---------+
| listing_id | price |
+------------+---------+
| 1 | 1500.00 |
| 2 | 1700.00 |
| 3 | 1800.00 |
| 4 | 1900.00 |
+------------+---------+
Amenities
+------------+------+
| listing_id | wifi |
+------------+------+
| 1 | 1 |
| 2 | 1 |
| 3 | 0 |
+------------+------+
Notice that I changed "id" to "listing_id" to make it clear what it was (using "id" as an attribute name is problematic anyways). Also, note that one listing doesn't have an entry in the Amenities table. Depending on your data, that may or may not be a concern (again, refer to the bottom for a discussion of your data model).
Based on this data, your averages should be as follows:
Listings with wifi average $1600 (Listings 1 and 2)
Listings without wifi (just 3) average 1800).
So the difference would be $200.
To achieve this result in SQL, it may be helpful to first get the average cost per amenity (whether wifi is offered). This would be obtained with the following query:
SELECT
Amenities.wifi AS has_wifi,
AVG(Billing.price) AS avg_cost
FROM Billing
INNER JOIN Amenities ON
Amenities.listing_id = Billing.listing_id
GROUP BY Amenities.wifi
which gives you the following results:
+----------+-----------------------+
| has_wifi | avg_cost |
+----------+-----------------------+
| 0 | 1800.0000000000000000 |
| 1 | 1600.0000000000000000 |
+----------+-----------------------+
So far so good. So now we need to calculate the difference between these 2 rows. There are a number of different ways to do this, but one is to use a CASE expression to make one of the values negative, and then simply take the SUM of the result (note that I'm using a CTE, but you can also use a sub-query):
WITH
avg_by_wifi(has_wifi, avg_cost) AS
(
SELECT Amenities.wifi, AVG(Billing.price)
FROM Billing
INNER JOIN Amenities ON
Amenities.listing_id = Billing.listing_id
GROUP BY Amenities.wifi
)
SELECT
ABS(SUM
(
CASE
WHEN has_wifi = 1 THEN avg_cost
ELSE -1 * avg_cost
END
))
FROM avg_by_wifi
which gives us the expected value of 200.
Now regarding your data model:
If both your Billing and Amenities table only have 1 row for each listing, it makes sense to combine them into 1 table. For example: Listings(listing_id, price, wifi)
However, this is still problematic, because you probably have a bunch of other amenities you want to model (pool, sauna, etc.) So you might want to model a many-to-many relationship between listings and amenities using an intermediate table:
Listings(listing_id, price)
Amenities(amenity_id, amenity_name)
ListingsAmenities(listing_id, amenity_id)
This way, you could list multiple amenities for a given listing without having to add additional columns. It also becomes easy to store additional information about an amenity: What's the wifi password? How deep is the pool? etc.
Of course, using this model makes your original query (difference in average cost of listings by wifi) a bit tricker, but definitely still doable.
I have a table with stock codes and quantity sold, but I would like to treat 2 different stock codes as one, the reason being is that one is imported and the other one locally produced but are the same product,
lets say
Product A - Imported, Stock code is abc123
Product A - Local, Stock code is aimp563
I want to sum over the quantity sold but treat the same product with and an imported stock code and local stock code as one. Is this possible?
Okay this is what I have
tbe table looks like
Product | StockCode | QtySold
Product A - Local | prdA001loc | 100
Product A - Imported | prdAImp7Z4 | 150
SELECT Product, SUM(QtySold) FROM tblA GROUP BY StockCode, Product
But this will just return the table as is. I would like this output:
Product | QtySold
Product A | 250
I believe that you need to update your DB schema to have reflect this information however if you need some naive solution you can use the following statement
SELECT substring(product, 1 , charindex('-',product)), SUM(QtySold)
FROM tblA GROUP BY substring(product, 1 , charindex('-',product))
note that the above statement assuming that all your products name will be similar to what is mentioned inside your question
In my journey to learn SQL, I'm writing various queries on an old database of mine, but getting into more complex things, I want to make sure I'm not over engineering this. I have a table Agent, with different agents offering different prices for cities. Multiple agents can serve the same city, each with different prices. I wanted to run a query which would return the total cost of hiring all of the agents for any given city, ordered by the most expensive.
WITH orderedPrices AS (
SELECT SUM(agtFMPrice)
OVER (PARTITION BY agtCity)
AS IX FROM Agent)
SELECT IX
FROM orderedPrices
ORDER BY IX DESC
I found that doing it without the view returned by orderedPrices, it wouldn't order the prices (I assume because it's an aggregate function, or whatever they're called). Did I do this in the best way I could have, or could it be simplified?
Also, if you're feeling particularly bored, go ahead and give me a new assignment/query to do on this table. I could use the practice.
What you have written in English doesn't seem to quite match qhat you have written in SQL.
English:
- One record per City
- One field per record, showing the total cost of all associated agents
SQL:
- One record per Agent
- One field per record, showing the total cost of all agents in the same city
AgentID | agtCity | agtFMPrice
---------+---------+------------
1 | 1 | 10
2 | 1 | 20
3 | 2 | 30
4 | 2 | 10
5 | 2 | 25
Results of SQL version Results of English version
------------------------ ----------------------------
30 30
30 65
65
65
65
If you want the English version, I'd do this...
SELECT
agtCity,
SUM(agtFMPrice) AS IX
FROM
Agent
GROUP BY
agtCity
ORDER BY
SUM(agtFMPrice) DESC
To assist performance, the table could (should?) also have an Index on (agtCity)
I am trying to write up a query for wordpress which will give me all the post_id's with the lowest fromprice field for each region. Now the trick is these are custom fields in wordpress, and due to such, the information is stored row based, so there is no region and fromprice columns.
So the data I have is (but of course containing a lot more rows):
Post_ID | Meta_Key | Meta_Value
1 | Region | Location1
1 | FromPrice | 150
2 | Region | Location1
2 | FromPrice | 160
3 | Region | Location2
3 | FromPrice | 145
The query I am endeavoring to build should return the post_id of the "lowest priced" matching post grouped by each region with results like:
Post_ID | Region | From Price
1 | Location1 | 150
3 | Location2 | 145
This will allow me to easily iterate the post_id's and print the required information, in fact, I would be just happy with returning post_id's if the rest is harder, I can then fetch the information independently if need be.
Thanks a lot, tearing my hair out over this one; don't often have to think about shifting results on their side from row based to column based that often, but this time I need it!
So you get an idea of the table structure I have, you can use the below as a guide. I thought I had this, but it turned out yes, this query prints out each distinct region WITH the lowest from price found attached to that post in the region, but the post_id is completely incorrect. I don't know why, it seems to be just getting the first result of the post_id and using that.
SELECT pm.post_id,
pm2.meta_value as region,
MIN(pm.meta_value) as price
FROM `wp_postmeta` pm
inner join `wp_postmeta` pm2
on pm2.post_id = pm.post_id
AND pm2.meta_key = 'region'
AND pm.meta_key = 'fromprice'
group by region
I suggest changing MIN(pm.meta_value) in your query to be MIN(CAST(pm.meta_value AS DECIMAL)). Meta_value is a character field, so your existing query will be returning the minimum string value, not the minimum numeric value; for example, "100" will be deemed to be lower than "21".
EDIT - amended CAST syntax.
It's hard to figure out without being able to execute the query, but would it help to just change your group by to:
group by pm.post_id, region