I have a MYSQL table called 'categories' from a project I inherited from someone else.
id parent_id name
1 NULL Travel
2 NULL Sleep
3 NULL Eat
4 NULL Bath
5 1 Prams
6 1 Travel Systems
7 2 Cots
8 3 High Chairs
The table is obviously a lot bigger than that, but you get the general idea. I have a MYSQL statement which brings together this table with other category, brand and product tables, but basically I want to list the parent category name from the above table with the sub-category in the statement. How do I do this?
My current statement is something like:
SELECT brands.name, products.name, categories.id, categories.name, brands.id,
FROM `products` , `brands` , `categories`
WHERE products.brand_id = brands.id
AND products.category_id = categories.id
AND brands.name = '$brand'
ORDER BY categories.name, products.name
How do I retrieve the parent category names in the results?
For example if the product is a Pram, how can I output "Travel". I could do seperate MYSQL statements in the loop but I want to avoid this. This is either a stupidly simple question (in which case I apologise for being brain dead) or a little more complicated! Thanks.
First you need to know the parent id of the current category and then get the name for that id, you could use a subquery in this way:
SELECT name FROM categories WHERE id = (SELECT pid FROM categories WHERE name = $brand)
EDIT: Since you need to get the category and subcategory names in the same row for a given subcategory id, try this:
SELECT sc.name AS subcategory, c.name AS category
FROM categories sc
LEFT JOIN categories c ON c.id = sc.parent
WHERE sc.id = $subcategory_id
Related
Let's say I have a table with the following fields...
MEMBER_ID (text)
CATEGORY1 (int)
CATEGORY2 (int)
CATEGORY3 (int)
CATEGORY4 (int)
...and let's say I have, like, 30+ more CATEGORY fields, all numbered accordingly. And in each category field, there is a numerical score.
Is there a query that could be used to populate a new table that looks like so...
MEMBER_ID
TOP_CATEGORY (the category name from the previous table with the
highest score for this MEMBER_ID)
SECOND_CATEGORY (the category name from the previous table with the
second-highest score for this MEMBER_ID)
THIRD_CATEGORY (the category name from the previous table with the
third-highest score for this MEMBER_ID)
...I know I could use CASE, but if I have a ton of CATEGORY fields, I assume that would get unwieldy. Do I have any other options?
Your best option in my opinion would be to normalise your database structure. Create a table of members, a table of categories and a table of scores by member & category. Having normalised, the problem you are trying to solve becomes a "top n per group" problem, followed by conditional aggregation. For example, if you follow the template for normalising that I have made in this demo, your query would look something like this:
select member_id,
max(case when `rank` = 1 then name end) as top_category,
max(case when `rank` = 2 then name end) as second_category,
max(case when `rank` = 3 then name end) as third_category
from (select n.member_id, c.name, s1.score, count(s2.score) + 1 as rank
from score s1
left join score s2 on s2.member = s1.member and s1.score < s2.score
join new_members n on n.id = s1.member
join category c on c.id = s1.category
group by n.member_id, c.name, s1.score
having count(s2.score) < 3) s
group by member_id
Once your database is normalised, adding new members, categories and scores becomes a lot easier, and queries to get the data out such as the above don't have to change at all.
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 a table for categories. This has a recursive relationship so that a category can become a subcategory of another category. The table looks like this:
id name short_desc long_desc tag_id parent_id
I wrote simple to get sql to find all level 1 categories:
SELECT * FROM category WHERE parent_id =0
Then I wrote a query to get all of the level 2 categories (where parent category doesn't have a parent)
SELECT * FROM category WHERE parent_id IN (SELECT id FROM category WHERE parent_id =0)
What I would like to do, is produce a column where is shows all category data and any relevant parent category.
Logically like this:
select all from category
if parent_id != 0, add the parent as a new row
repeat 2 until all parents have been accounted for.
The result should look something like this:
id name short_desc long_desc tag_id parent_name parent_name_2
if the parent_name is null / empty, then parent_name should remain empty. if there is a parent_name id in the field, then check to see if there is a parent_name_2 and if so, populate both columns, if not then only populate parent_name.
I do have the option of coding this in jquery or php which I have a good idea how to do. However, I am sure that I can get the data I need from a good SQL query.
Any help would be greatly appreciated.
Kind Regards
Nick
Here's one option using multiple outer joins:
select c.*,
case when c2.id is not null then c2.name end parent_name,
case when c3.id is not null then c3.name end parent_name_2
from category c
left join category c2 on c.parent_id = c2.id
left join category c3 on c2.parent_id = c3.id
SQL Fiddle Demo
I am creating a MySQL database. I have a column named, name of the product. The product has one Main Category. However, it can belong to n-number of sub categories. I need to map these sub categories to that product. How can I do that?
Table1 - Product Info
Columns - ID, Name, MainCategory, SubCategory (Not Sure Exactly)
Table2 - MainCategory
Columns - ID, Name
Table3 - SubCategory
Columns - ID, Name
Table1 has 1-to-1 relationship to Table2.
How do I map Table1 to Table3? Am I doing this wrong?
Thought: I want to do it in the manner so that whenever I click on any subcategory name on a website, I get a list of all the products under that category. Just like it happens in Online Stores Website.
Example: The product External Hard Drive will come under Computer Accessories. But I want to give it sub-categories like offer_running, 500GB, SomeCompanyName, black etc.
Hope I explained my question. Please help me in the designing of database. I have got all the basics of DBMS, but I don't know how to involve keywords and to store & map them in a database.
How about the following structure:
Table1 - Product Info
Columns - ID, Name, Main_Category_ID
Table2 - Category
Columns - ID, Name
Table3 - Product_Category
Columns - ID, Product_ID, Category_ID, Name
Then you could use the following query to get all of the get all of the information:
SELECT p.*, c.Name
FROM [Product Info] p
INNER JOIN Product_Category pc ON p.ID = pc.Product_ID
INNER JOIN Category c ON pc.Category_ID = c.ID
Notice that in the Product Info table I added a Main_Category_ID field. If you really need to identify the main category then this would work:
SELECT p.ID, p.Name, NULL AS MainCat, c.Name AS SubCat
FROM [Product Info] p
INNER JOIN Product_Category pc ON p.ID = pc.Product_ID
INNER JOIN Category c ON pc.Category_ID = c.ID
UNION
SELECT p.ID, p.Name, c.Name AS MainCat, NULL AS SubCat
FROM [Product Info] p
INNER JOIN Category c ON p.Main_Category_ID = c.ID
First of all, if table 1 and table 2 have a 1-1 relationship, there is no need for having two separate tables. This will make query processing faster and will eliminate the need for an extra join.
Can you clarify what the ID column in table 3 refers to? Is this an unique ID for table 3 or the ID from table 1?
If former is the case, then you need to have the ID column of table 1 as the foreign key in table 3. That will resolve your issues.
Hope that helps.