I looked and tried various examples, but still not get the results I need.
With have a table called "item" which has metadata about media (books, vidoes, mp3 ,etc"
and a table "item_format" with the URL of the video
and Table with "categories"
and a relational to called "categories_item"
I want to find all the record on our youTube videos sorted by categories. so that if you look for "parenting" we get list a list a youTube and the title.
parenting https://youtube/v/K8cJKirMo-A Love is The Tey
https://youtube/v/uodqINpEC_w Discipline
https://youtube/v/Ko-ZboCzR64 Become Her Friend
and so on, listing all the categories assigned
item.media-type LIKE '%video%'
item
===============
item_id media_type title
1 video/teachings Discipline
2 video/news December Update
3 video/landscape Quad Copter Noni Field
item_format
=================
item_format_id item_id format
1 2 https://youtube/v/K8cJKirMo-A
2 4 https://youtube/v/uodqINpEC_w
category
=================
category_id item_id name
1 2 parenting
2 4 ethics
category_item # the bridging table between item/category
=================
category_item_id category_id item_id
1 2 2
2 4 3
I tried things like this but get errors, frankly out my depth here
select item.title, item_format.format
from item i
left join item_format if
on i.item_id = if.item_id
left join category_item ci
on i.item_id = ci.item_id
left join category c
on ci.category_id = category_id
where i.media_type LIKE '%video5'
order by c.name
I can't get to first base
Unknown column 'item.title' in 'field list' #line 1
your query is ok , but a small change need. you use table alias. in first line just use table alias instead of table name
select i.title, if.format,c.name
from item i
left join item_format if on (i.item_id = if.item_id)
left join category_item ci on (i.item_id = ci.item_id)
left join category c on (ci.category_id = c.category_id)
where i.media_type LIKE '%video5'
order by c.name
you have to provide alias once you have given it:
see if it works:
select i.title, if.format,c.name
from item i
inner join item_format if
on i.item_id = if.item_id
inner join category c
on i.item_id=c.item_id
inner join category_item ci
on c.category_id=ci.category_id
where i.media_type LIKE '%video%'
order by c.name
or this:
select i.title,if.format,c.name
from item i,item_format if,category c, category_item ci
where
i.item_id=if.item_id and
i.item_id=c.item_id and
c.category_id=ci.category_id
order by c.name;
Related
I have two tables
CATEGORY
id category parent_id
1 Electronic
2 Furniture
3 Phone 1
4 LCD 1
5 Watch 1
6 Desk 2
ORDER
id customer product category_id
1 John Smartphone 3
2 Marry Montior 4
3 King Wood-Desk 6
I want to find all of electronic result by child_id.
Like this..
SELECT product FROM order WHERE category_id = (category.id = 1)
RESULT
product
Smartphone
Monitor
Is there any expression like this in MySQL?
You can use a join for this. You also will need to encapsulate the order table name with backticks because order is reserved (alternatively you could rename that table to save yourself from encapsulating everytime).
SELECT product FROM `order` as o
join category as c
on o.category_id = c.id
WHERE c.parent_id = 1
The on tells the DB what to data to join on. The as creates an alias so the full table name doesn't need to be written out everytime. (The as also is optional, I find it easier to read, FROM `order` o would be the same)
An alternative approach could be using a sub-query:
SELECT product
FROM `order`
WHERE category_id in (SELECT id FROM CATEGORY where parent_id = 1)
You have to use INNER JOIN
SELECT order.product
FROM order
INNER JOIN category
ON order.category_id = category.id
WHERE category.parent_id = 1
The ON keyword shows what columns will be compare between these tables. When you make a JOIN you need to put the table name before the column name separated with "." because it is possible to exist a column with the same name in both tables.
For the sake of clarity and this question i will rename the tables so it is a bit clearer for everybody and explain what i want to achieve:
There is an input form with options that return categories ID's. If a 'Product' has 'Category', i want to return/find the 'Product' which lets say has multiple categories(or just 1) and all of its categories are inside the array that is passed from the form.
Products table
ID Title
1 Pizza
2 Ice Cream
Categories table
ID Title
1 Baked food
2 Hot food
ProductsCategories table
ID ProductId CategoryId
1 1 1
2 1 2
So if i pass [1,2] the query should return Product with id 1 since all ProductsCategories are inside the requested array, but if i pass only 1 or 2, the query should return no results.
Currently i have the following query which works, but for some reason if i create a second Product and create a ProductCategory that has a CategoryId same as the first product, the query returns nulll...
SELECT products.*
FROM products
JOIN products_categories
ON products_categories.product_id= products.id
WHERE products_categories.category_id IN (1, 2)
HAVING COUNT(*) = (select count(*) from products_categories pc
WHERE pc .product_id = products.id)
All help is deeply appretiated! Cheers!
In order to match all values in IN clause, you just need to know in addition the number of passed categories which you must use it in HAVING clause:
SELECT
p.*,
GROUP_CONCAT(c.title) AS categories
FROM
Products p
INNER JOIN ProductsCategories pc ON pc.productId = p.ID
INNER JOIN Categories c ON c.ID = pc.categoryId
WHERE
pc.categoryId IN (1,2)
GROUP BY
p.id
HAVING
COUNT(DISTINCT pc.categoryId) = 2 -- this is # of unique categories in IN clause
So in case IN (1,2) result is:
+----+-------+---------------------+
| id | title | categories |
+----+-------+---------------------+
| 1 | Pizza | Baked Food,Hot Food |
+----+-------+---------------------+
1 row in set
In case IN (1,3) result is Empty set (no results).
#mitkosoft, thanks for your answer, but sadly the query is not producing the needed results. If the product's categories are partially in the passed categories the product is still returned. Additionally i might not know how many parameters are sent by the form.
Luckily I managed to create the query that does the trick and works perfectly fine (at least so far)
SELECT products.*,
COUNT(*) as resultsCount,
(SELECT COUNT(*) FROM products_categories pc WHERE pc.product_id = products.id) as categoriesCount
FROM products
JOIN products_categories AS productsCategories
ON productsCategories.product_id= products.id
WHERE productsCategories.category_id IN (7, 15, 8, 1, 50)
GROUP BY products.id
HAVING resultsCount = categoriesCount
ORDER BY amount DESC #optional
That way the query is flexible and gives me exactly what I needed! - Only those products that have all their categories inside the search parameters(not partially).
Cheers! :)
I have 3 tables as follows :
Table 1: Product
id_product [Primary Key],added_time.
Table 2: Category
id_category [Primary Key],Category_name.
Table 3: product_category
id_category,id_product [Both Foreign Keys]
I want to pull Data as
Category_name,No Of Products in this Category,Last time when product was added to Category(Latest product added_time).
You could use this SQL:
SELECT Category.Category_name,
Count(DISTINCT Product.id_product) AS num_products,
Max(Product.added_time) last_added_time
FROM Category
LEFT JOIN product_category
ON product_category.id_category = Category.id_category
LEFT JOIN Product
ON Product.id_product = product_category.id_product
GROUP BY Category.Category_name;
Note that by using LEFT JOIN you will be certain to list all categories even those for which no products exist. If you don't want those, replace both LEFT keywords with INNER.
Note also that in standard SQL you need to GROUP BY any columns you mention in the SELECT list, unless they are aggregated, like with MAX or COUNT.
SELECT C.`Category_name`,
(SUM(IF(P.`id_product`IS NULL,0,1))) AS No_of_Products,
MAX(P.`added_time`) AS Latest_time
FROM
Category C
LEFT JOIN
product_category P_C ON C.`id_category` = P_C.`id_category`
LEFT JOIN
Product P ON P.`id_product` = P_C.`id_product`
GROUP BY C.`id_category`
Hope this helps.
Suppose I have a Product table, and a
id product
1 Apple
2 Bag
3 Cat
4 Ducati
and a Cart table
id user_id product_id
1 1 2
2 1 3
3 2 1
4 3 1
So, I want to look at a particular user and see what he/she does NOT have in their Cart.
In other words, in the above example
SELECT ...... WHERE user_id=1 .....
would return Apple and Ducati because User 1 already has Bag and Cat.
(This may well duplicate another question but there are so many variations I couldn't find the exact match and put in these simple terms may help)
Perform a left join from product to all products purchased by user1, which can be retrieved with a subselect in the join. This will cause all product id's that are not in user1's care to have null product ids. The where clause will select all null product id's meaning they will not have been in a users cart, essentially filtering purchased items.
select p.name
from product p
left join (select product_id, user_id
from cart where user_id = 1)
c
on p.id = c.product_id
where c.product_id is null;
SQL Fiddle: http://sqlfiddle.com/#!2/5318eb/17
Select
*
From Product p
Where p.id Not In
(
Select c.product_id
From Cart c
Where User ID = ____
)
SELECT product FROM product_table
WHERE product NOT IN
(SELECT product_id FROM cart_table WHERE user_id = 1);
This will give you all product for all users which are not in there cart.
select c.user_id,a.Product
from cart c Cross Join product a
left Join
cart b on b.product_id=a.id and c.user_id=b.user_Id
where b.product_id is null
group by c.user_id,a.Product
Sql Fiddle Demo
I have a table "articles" with columns and data:
article_id title body
1 This is the title This is the body text
2 Another title Another body text
Another table "category" with columns and data:
category_id category
1 localnews
2 visible
3 first10
And a table "categories" with columns and data:
categories_id article_id category_id
1 1 1
2 1 2
3 1 3
4 2 1
5 2 3
I want to SELECT the row(s) WHERE categories.category_id = 1 AND =2 AND =3
I'm using:
SELECT articles.article_id, articles.title, articles.body,
categories.article_id, categories.category_id
FROM articles, categories
WHERE articles.article_id = categories.article_id
AND categories.article_id = 1
AND categories.article_id = 2
AND categories.article_id = 3
but it doesn't work. Obviously mySQL needs another syntax.
Can someone help?
Thanks
SELECT
Articles.article_id,
COUNT( Categories.article_id ) AS total
FROM CategoryArticles
LEFT JOIN Articles USING (article_id)
WHERE
CategoryArticles.category_id IN (1,2,3)
GROUP BY CategoryArticles.article_id
HAVING total = 3
I used a bit different names for table because in your example the distinction between category and categories is hard to notice.
An column of a row cannot be 1, 2 or 3 at the same time, which is what AND stipulates. Use OR in your WHERE condition. Better yet - for readability - you can use IN:
SELECT ...
WHERE `categories`.`article_id` IN(1,2,3)
In addition to the commonly used IN() and using a HAVING count, I would be interested in the performance difference by doing a multiple-join as follows...
SELECT STRAIGHT_JOIN
articles.article_id,
articles.title,
articles.body
FROM
categories c1
JOIN articles
on c1.article_id = articles.article_id
JOIN categories c2
on c1.article_id = c2.article_id
AND c2.category_id = 2
JOIN categories c3
on c1.article_id = c3.article_id
AND c3.category_id = 3
WHERE
c1.Category_ID = 1
Yes, this may look obscure, but lets think about it... by doing a join FIRST on the categories table where ONE of your specific categories -- THIS FIRST FROM instance of categories should be representative of whichever category would have the smallest granularity. Ex: Your categories of Local News, Visible and First 10. Local news would probably have the most entries, while Visible and First 10 would have even less... of those, which would have even the smallest number of records. Use THIS category as the where clause.
So, say you have 100,000 articles, and 90,000 are in local news, 45,000 in Visible, and 12,000 in First 10. By starting your query on only those in the 12,000, you are eliminating most of the data.
By then joining to the articles table, and categories AGAIN as alias C2 and C3 respectively based on the other conditions, if found, done, if not, its excluded.
Again, I'm wondering the performance impact. I would also have a compound index on the categories table on both (article_id, category_id)
The value cannot be all three values simultaneously, so you'd better use an IN clause in your WHERE to define which you want to return. Give you've already got a join condition there, you'd want to move that to an ON clause instead as well; ie:
SELECT articles.article_id, articles.title, articles.body, categories.article_id, categories.category_id
FROM articles
INNER JOIN categories ON articles.article_id = categories.article_id
WHERE categories.article_id IN ( 1, 2, 3 )
Of course, you can go to the next step and do:
SELECT articles.article_id, articles.title, articles.body, category.category
FROM articles
INNER JOIN categories ON articles.article_id = categories.article_id
INNER JOIN category ON categories.category_id = category.category_id
WHERE categories.article_id IN ( 1, 2, 3 )
If instead you wanted to show only articles that appear in all three categories, then you could take an approach like:
SELECT articles.article_id, articles.title, articles.body
FROM articles
INNER JOIN categories AS c1
ON articles.article_id = c1.article_id
AND c1.category_id = 1
INNER JOIN categories AS c2
ON articles.article_id = c2.article_id
AND c2.category_id = 2
INNER JOIN categories AS c3
ON articles.article_id = c3.article_id
AND c3.category_id = 3