i have a table company row like this :
id(int) |name(string) |maincategory(int) |subcategory(string)
1 |Google |1 |1,2,3
2 |yahoo |4 |4,1
and other table category like:
id(int) |name(string)
1 |Search
2 |Email
3 |Image
4 |Video
i want to join tow table by company.subcategory = category.id
is it possible in sql ?
Start by splitting your subcategory column. In the end you should have an additional company_category table with company_id and category_id as columns.
company_id(int) |category_id(int)
1 |1
1 |2
1 |3
2 |4
2 |1
Your design is invalid. You shoud have another table called companySubcategories or something like that.
This table shoud have two columns companyId an categoryId.
Then your select would look like this:
select <desired fields> from
company c
join companySubcategories cs on cs.companyId = cs.id
join category ct on ct.id = cs.categoryId
you can do like below...
select * from
company c, category cc
where c. subcategory like '%'||cc.id||'%';
it is working as expected in oracle database ..
You could introduce a new table company_subcategory to keep track of subcategories
id (int) | subcategory(int)
1 | 1
1 | 2
1 | 3
2 | 1
2 | 4
then you would be able to run select as
select company.name AS company, category.name AS category
FROM company
JOIN company_subcategory
ON company.id = company_subcategory.company
JOIN category
ON company_subcategory.subcategory = category.id;
to get
+---------+----------+
| company | category |
+---------+----------+
| google | search |
| google | email |
| google | image |
| yahoo | search |
| yahoo | video |
+---------+----------+
SELECT *
FROM COMPANY CMP, CATEGORY CT
WHERE (SELECT CASE
WHEN INSTR(CMP.SUB_CATEGORY, CT.ID) > 0 THEN
'TRUE'
ELSE
'FALSE'
END
FROM DUAL) = 'TRUE'
This query looks for the ID in the SUB_CATEGORY, using the INSTR function.
In case it does exist, the row is returned.
The output is as below
ID NAME MAIN_CATEGORY SUB_CATEGORY ID NAME
1 Google 1 1,2,3 1 Search
1 Google 1 1,2,3 2 Email
1 Google 1 1,2,3 3 Image
2 yahoo 2 4,1 1 Search
2 yahoo 2 4,1 4 Video
Hope it helps.
However, I suggest you avoid this type of entries, as an ID should have separate entries and not combined entries. This may create problems in future, so it would be better to avoid it now.
Related
I want to be able to filter out groups where the values aren't the same. When doing the query:
SELECT
category.id as category_id,
object.id as object_id,
object.value as value
FROM
category,
object
WHERE
category.id = object.category
We get the following results:
category_id | object_id | value
-------------+-----------+-------
1 | 1 | 1
1 | 2 | 2
1 | 3 | 2
2 | 4 | 3
2 | 5 | 2
3 | 6 | 1
3 | 7 | 1
The goal: Update the query so that it yields:
category_id
-------------
1
2
In other words, find the categories where the values are different from the others in that same category.
I have tried many different methods of joining, grouping and so on, to no avail.
I know it can be done with multiple queries and then filter with a little bit of logic, but this is not the goal.
You can use aggregation:
SELECT o.category as category_id
FROM object o
GROUP BY o.category
HAVING MIN(o.value) <> MAX(o.value);
You have left the FROM clause out of your query. But as written, you don't need a JOIN at all. The object table is sufficient -- because you are only fetching the category id.
I Have a query that finds a table, here's an example one.
Name |Age |Hair |Happy | Sad |
Jon | 15 | Black |NULL | NULL|
Kyle | 18 |Blonde |YES |NULL |
Brad | 17 | Blue |NULL |YES |
Name and age come from one table in a database, hair color comes from a second which is joined, and happy and sad come from a third table.My goal would be to make the first line of the chart like this:
Name |Age |Hair |Happy |Sad |
Jon | 15 |Black |Yes |Yes |
Basically I want to get rid of the rows under the first and get the non NULL data joined to the right. The problem is that there is no column where the Yes values are on the Jon row, so I have no idea how to get them there. Any suggestions?
PS. With the data I am using I can't just put a 'YES' in the 'Jon' row and call it a day, I would need to find the specific value from the lower rows and somehow get that value in the boxes that are NULL.
Do you just want COALESCE()?
COALESCE(Happy, 'Yes') as happy
COALESCE() replaces a NULL value with another value.
If you want to join on a NULL value work with nested selects. The inner select gets an Id for NULLs, the outer select joins
select COALESCE(x.Happy, yn_table.description) as happy, ...
from
(select
t1.Happy,
CASE WHEN t1.Happy is null THEN 1 END as happy_id
from t1 ...) x
left join yn_table
on x.xhappy_id = yn_table.id
If you apply an ORDER BY to the query, you can then select the first row relative to this order with WHERE rownum = 1. If you don't apply an ORDER BY, then the order is random.
After reading your new comment...
the sense is that in my real data the yes under the other names will be a number of a piece of equipment. I want the numbers of the equipment in one row instead of having like 8 rows with only 4 ' yes' values and the rest null.
... I come to the conclusion that this a XY problem.
You are asking about a detail you think will solve your problem, instead of explaining the problem and asking how to solve it.
If you want to store several pieces of equipment per person, you need three tables.
You need a Person table, an Article table and a junction table relating articles to persons to equip them. Let's call this table Equipment.
Person
------
PersonId (Primary Key)
Name
optional attributes like age, hair color
Article
-------
ArticleId (Primary Key)
Description
optional attributes like weight, color etc.
Equipment
---------
PersonId (Primary Key, Foreign Key to table Person)
ArticleId (Primary Key, Foreign Key to table Article)
Quantity (optional, if each person can have only one of each article, we don't need this)
Let's say we have
Person: PersonId | Name
1 | Jon
2 | Kyle
3 | Brad
Article: ArticleId | Description
1 | Hat
2 | Bottle
3 | Bag
4 | Camera
5 | Shoes
Equipment: PersonId | ArticleId | Quantity
1 | 1 | 1
1 | 4 | 1
1 | 5 | 1
2 | 3 | 2
2 | 4 | 1
Now Jon has a hat, a camera and shoes. Kyle has 2 bags and one camera. Brad has nothing.
You can query the persons and their equipment like this
SELECT
p.PersonId, p.Name, a.ArticleId, a.Description AS Equipment, e.Quantity
FROM
Person p
LEFT JOIN Equipment e
ON p.PersonId = e.PersonId
LEFT JOIN Article a
ON e.ArticleId = a.ArticleId
ORDER BY p.Name, a.Description
The result will be
PersonId | Name | ArticleId | Equipment | Quantity
---------+------+-----------+-----------+---------
3 | Brad | NULL | NULL | NULL
1 | Jon | 4 | Camera | 1
1 | Jon | 1 | Hat | 1
1 | Jon | 5 | Shoes | 1
2 | Kyle | 3 | Bag | 2
2 | Kyle | 4 | Camera | 1
See example: http://sqlfiddle.com/#!4/7e05d/2/0
Since you tagged the question with the oracle tag, you could just use NVL(), which allows you to specify a value that would replace a NULL value in the column you select from.
Assuming that you want the 1st row because it contains the smallest age:
- wrap your query inside a CTE
- in another CTE get the 1st row of the query
- in another CTE get the max values of Happy and Sad of your query (for your sample data they both are 'YES')
- cross join the last 2 CTEs.
with
cte as (
<your query here>
),
firstrow as (
select name, age, hair from cte
order by age
fetch first row only
),
maxs as (
select max(happy) happy, max(sad) sad
from cte
)
select f.*, m.*
from firstrow f cross join maxs m
You can try this:
SELECT A.Name,
A.Age,
B.Hair,
C.Happy,
C.Sad
FROM A
INNER JOIN B
ON A.Name = B.Name
INNER JOIN C
ON A.Name = B.Name
(Assuming that Name is the key columns in the 3 tables)
Postgresql Database
Table User
-----------
ID | Name
1 | John
2 | Bob
3 | Sarah
Table Photo
-------------
ID | Caption
1 | Vacation
2 | Birthday
3 | Christmas
Table Comment
--------------
ID | User ID | Photo ID| Text
1 | 1 | 1 | Mexico Looks Great
2 | 2 | 1 | Sure Does
3 | 3 | 1 | Too Hot
4 | 1 | 2 | Look at that cake
5 | 3 | 2 | No ice cream?
6 | 1 | 3 | So Happy
Desire: I want to get all the photos that ONLY John(1) and Sara(3) commented on.
How do I build a SQL query that looks for photos that only have comments from user #1 and user #3, I want to EXCLUDE results where more(or less) than those two commented on.
The clearest and most readable way, is the Photos containing comments by:
User1 Intersect User2 Except Any other user
This SQL Fiddle and query will return that:
SELECT *
FROM Photo
WHERE ID IN (
SELECT "Photo ID" FROM Comment WHERE "User ID" = 1
INTERSECT
SELECT "Photo ID" FROM Comment WHERE "User ID" = 3
EXCEPT
SELECT "Photo ID" FROM Comment WHERE "User ID" NOT IN (1, 3)
)
lets do three joins, one for john, one for sara, one for everyone else. Then we'll limit what we get back with the where clause.
select p.*
from photo p
left join comment john on john.photo_id=p.photo_id and john.user_id=1
left join comment sara on sara.photo_id=p.photo_id and sara.user_id=3
left join comment everyone_else on everyone_else.photo_id=p.photo_id and everyone_else.user_id<>3 and everyone_else.user_id<>1
where
everyone_else.id is null
and john.id is not null
and sara.id is not null
There are a couple of ways to do this. One is to use count with case:
select photoid
from comment
group by photoid
having count(distinct userid) = 2
and count(case when userid not in (1,3) then 1 end) = 0
SQL Fiddle Demo
Basically, make sure 2 users have commented and then make sure only user 1 or 3 commented.
You could use an intersection to find only the common photos, which would exclude photos commented by John but not Sarah, or vice versa
select photo_id from comment where user_id = 1
intersect
select photo_id from comment where user_id = 3
I have a table in MS Access which looks basically like this:
Table Name : Customer_Categories
+----------------------+------------+-------+
| Email | CategoryID | Count |
+----------------------+------------+-------+
| jim#example.com | 10 | 4 |
+----------------------+------------+-------+
| jim#example.com | 2 | 1 |
+----------------------+------------+-------+
| simon#example.com | 5 | 2 |
+----------------------+------------+-------+
| steven#example.com | 10 | 16 |
+----------------------+------------+-------+
| steven#example.com | 5 | 3 |
+----------------------+------------+-------+
In this table there are ≈ 350,000 records. The characteristics are this:
Duplicate values for Email, CategoryID and Count
Count refers to the number of times this customer has ordered from this category
What I want
I want to create a table that consists of a unique email address along with the CategoryID this customer has purchased from the most.
So the above example would be:
+----------------------+------------+
| Email | CategoryID |
+----------------------+------------+
| jim#example.com | 10 |
+----------------------+------------+
| simon#example.com | 5 |
+----------------------+------------+
| steven#example.com | 10 |
+----------------------+------------+
What I have tried
I have written a query that achieves what I want:
SELECT main.Email, (SELECT TOP 1 CategoryID
FROM Customer_Categories
WHERE main.Email = Email
GROUP BY CategoryID
ORDER BY MAX(Count) DESC, CategoryID ASC) AS Category
FROM Customer_Categories AS main
GROUP BY main.Email;
This works a treat and does exactly what I want. It returns results in around 8 seconds. However I need this data in a new table because I then want to update another table with the categoryID. When I add INTO Customer_Favourite_Categories after the sub-query to add this data to a new table rather than just return the result set and run the query it never finishes. I've left it running for about 45 minutes and it does nothing.
Is there any way around this?
If select into doesn't work, use insert into:
create table Customer_Favorite_Categories (
email <email type>,
FavoriteCategory <CategoryId type>
);
insert into Customer_Favorite_Categories
SELECT main.Email, (SELECT TOP 1 CategoryID
FROM Customer_Categories
WHERE main.Email = Email
GROUP BY CategoryID
ORDER BY MAX(Count) DESC, CategoryID ASC) AS Category
FROM Customer_Categories AS main
GROUP BY main.Email;
Try this:
SELECT Distinct(Email),Max(CategoryID )
FROM Customer_Categories group by Email
I use sub-queries for this quite frequently. Your query in "What I have tried" is close, but just a little off in syntax. Something like the following should get what you are after. Count is in square-brackets since it's a reserved word in SQL. The spacing I use in my SQL is conventional, so edit to your liking.
SELECT Email,
CategoryID
FROM MyTable AS m,
(
SELECT Email,
MAX( [Count] ) AS mc
FROM MyTable
GROUP BY Email
) AS f
WHERE m.Email = f.Email
AND m.[Count] = f.mc;
I am representing itemsets in SQL (SQLite, if relevant). My tables look like this:
ITEMS table:
| ItemId | Name |
| 1 | Ginseng |
| 2 | Honey |
| 3 | Garlic |
ITEMSETS:
| ItemSetId | Name |
| ... | ... |
| 7 | GinsengHoney |
| 8 | HoneyGarlicGinseng |
| 9 | Garlic |
ITEMSETS2ITEMS
| ItemsetId | ItemId |
| ... | .... |
| 7 | 1 |
| 7 | 2 |
| 8 | 2 |
| 8 | 1 |
| 8 | 3 |
As you can see, an Itemset may contain several Items, and this relationship is detailed in the Itemset2Items table.
How can I check whether a new itemset is already in the table, and if so, find its ID?
For instance, I want to check whether "Ginseng, Garlic, Honey" is an existing itemset. The desired answer would be "Yes", because there exists a single ItemsetId which contains exactly these three IDs. Note that the set is unordered: a query for "Honey, Garlic, Ginseng" should behave identically.
How can I do this?
I would recommend that you start by placing the item sets that you want to check into a table, with one row per item.
The question is now about the overlap of this "proposed" item set to other itemsets. The following query provides the answer:
select itemsetid,
from (select coalesce(ps.itemid, is2i.itemid) as itemid, is2i.itemsetid,
max(case when ps.itemid is not null then 1 else 0 end) as inProposed,
max(case when is2i.itemid is not null then 1 else 0 end) as inItemset
from ProposedSet ps full outer join
ItemSets2items is2i
on ps.itemid = is2i.itemid
group by coalesce(ps.itemid, is2i.itemid), is2i.itemsetid
) t
group by itemsetid
having min(inProposed) = 1 and min(inItemSet) = 1
This joins all the proposed items with all the itemsets. It then groups by the items in each item set, giving a flag as to whether the item is in the set. Finally, it checks that all items in an item set are in both.
Sounds like you need to find an ItemSet that:
contains all the Items in your wanted list
doesn't contain any other Items
This example will return the ID of such an itemset if it exists.
Note: this solution is for MySQL, but it should work in SQLite once you change #variables into something SQLite understands, e.g. bind variables.
-- these are the IDs of the items in the new itemset
-- if you add/remove some, make sure to change the IN clauses below
set #id1 = 1;
set #id2 = 2;
-- this is the count of items listed above
set #cnt = 2;
SELECT S.ItemSetId FROM ItemSets S
INNER JOIN
(SELECT ItemsetId, COUNT(*) as C FROM ItemSets2Items
WHERE ItemId IN (#id1, #id2)
GROUP BY ItemsetId
HAVING COUNT(*) = #cnt
) I -- included ingredients
ON I.ItemsetId = S.ItemSetId
LEFT JOIN
(SELECT ItemsetId, COUNT(*) as C FROM ItemSets2Items
WHERE ItemId NOT IN (#id1, #id2)
GROUP BY ItemsetId
) A -- additional ingredients
ON A.ItemsetId = S.ItemSetId
WHERE A.C IS NULL
See fiddle for MySQL.