I have three simple tables:
Category which stores my list of different types of categoriesCategory Table
Items, which stores my items:
JunctionTable table, as a connection between category and items - relation N:M
item_list_category junction table
So my problem is, I would like to create select which will select data from all mentioned tables. First I tried this:
SELECT item_list_id, ARRAY_AGG(category_id) AS array_category
FROM item_list_category
WHERE item_list_id = 1
GROUP BY item_list_id;
With this result:
Attempt 1
Then I wanted to Join tables:
SELECT item_list_id, ARRAY_AGG(category_id) AS array_category
FROM item_list_category
WHERE item_list_id = 1
GROUP BY item_list_id;
This is result, but this is not obviously what I need.Attempt 2
I expected for instance: {"Dětské", "Misteriozní"} etc.
Related
I am trying to create a table that has columns called user_id and top5_foods (binary column). I currently have two tables, one has all of the user_ids and the foods associated with those user_ids and one table that only contains the top5 foods according to a type of calculation to select the top5 foods.
The table that I am trying to create if to have the column of the user_id and if at least one of their favorite foods is in the top_5_food table, put the value of the top5_foods as 1 and if not, 0.
Something like the following:
user_id top5_foods
----------------------
34223 1
43225 0
34323 1
I have tried to use the CASE command but it just duplicated the user_ids and mark 1 or 0 whenever it finds a food that is in the top_5_foods table. But I don't want it to duplicate. Could you please help ?
Thank you very much
If I understand correctly, a left join and aggregation:
select uf.user_id,
(count(t.food_id) > 0) as top5_foods
from user_foods uf left join
top5_foods t
on uf.food_id = t.food_id
group by uf.user_id;
I'm trying to create a summarised result set joining two tables.
The first table (main and multi row) contains say the following columns:
trans_id,
trans_type_id
The second table (one row only) contains:
from_trans_type_id,
to_trans_type_id
I'm trying to join the two tables so that from_trans_type_id = trans_type_id and to_trans_type_id = trans_type_id and get the relevant trans_id values
I've tried self joining and derived joins to no effect.
The end result is that I'm looking to get a result set that looks something like this:
trans_id as from_trans_id, from_trans_type_id, trans_id as to_trans_id, to_trans_type_id
data is:
you can use join with multiple instance of firsttable
select b.trans_id as from_trans_id, from_trans_type_id, c.trans_id as to_trans_id, to_trans_type_id
from secondtable a
inner join firsttable b on a.from_trans_type_id=b.trans_type_id
inner join firsttable c on a.to_trans_type_id=c.trans_type_id
I have a 3 Tables like this:
Table 1: Category (ID, Description)
Table 2: SubCategory (ID, Description, CategoryParent_ID)
Table 3: Items (ID, SubCategory_ID, Info, Documentation, etc...)
where SubCategory_ID in items table refers to SubCategory Table, & this last one refers to Category Table by CategoryParent_ID.
enter image description here
I want to make a query, that:
When I select a Category from Table 1, Every item in Table 3 that related to this Category is shown (via SubCategory)
Example: I select IT Equipment from table 1
data shown must be: Every item in table 3 that is related to Table 2 AND Table 2 get its reference from TABLE 1
You probably want to look into joins.
SELECT *
FROM tableOne, tableTwo, tableThree
WHERE tableOne.ID = tableTwo.CategoryParent_ID AND tableTwo.ID = tableThree.SubCategory_ID
You can also avoid these joins in the "where" clause by explicitly placing them in the "from" clause.
For example (jarlh's way):
SELECT *
FROM tableOne
INNER JOIN tableTwo ON tableOne.ID = tableTwo.CategoryParent_ID
INNER JOIN tableThree ON tableTwo.ID = tableThree.SubCategory_ID
Here's some info:
https://www.w3schools.com/sql/sql_join.asp
I am new to SQL and I would like to get some insights for my problem
I am using the following query,
select id,
pid
from assoc
where id in (100422, 100414, 100421, 100419, 100423)
All these id need not have pid, some doesn't and some has pid. Currently it skips the records which doesn't have pid.
I would like a way which would show the results as below.
pid id
-----------
703 100422
313 100414
465 100421
null 100419
null 100423
Any help would be greatly appreciated. Thanks!
Oh, I think I've got the idea: you have to enumerate all the ids and corresponding pids. If there's no corresponding pid, put null (kind of outer join). If it's your case, then Oracle solution can be:
with
-- dummy: required ids
dummy as (
select 100422 as id from dual
union all select 100414 as id from dual
union all select 100421 as id from dual
union all select 100419 as id from dual
union all select 100423 as id from dual),
-- main: actual data we have
main as (
select id,
pid
from assoc
-- you may put "id in (select d.id from dummy d)"
where id in (100422, 100414, 100421, 100419, 100423))
-- we want to print out either existing main.pid or null
select main.pid as pid,
dummy.id as id
from dummy left join main on dummy.id = main.id
id is obtained from other table and assoc only has pid associated with id.
The assoc table seems to be the association table used to implement a many-to-many relationship between two entities in a relational database.
It contains entries only for the entities from one table that are in relationship with entities from the other table. It doesn't contain information about the entities that are not in a relationship and some of the results you want to get come from entities that are not in a relationship.
The solution for your problem is to RIGHT JOIN the table where the column id comes from and put the WHERE condition against the values retrieved from the original table (because it contains the rows you need). The RIGHT JOIN ensures all the matching rows from the right side table are included in the result set, even when they do not have matching rows in the left side table.
Assuming the table where the id column comes from is named table1, the query you need is:
SELECT assoc.id, assoc.pid
FROM assoc
RIGHT JOIN table1 ON assoc.id = table1.id
WHERE table1.id IN (100422, 100414, 100421, 100419, 100423)
I'm new to SQL. I have a simple problem with getting the results from two different tables.
I have two tables in a database. The first table has a column with an id reference, which corresponds to rows in the second table. What SELECT do I need to perform to get a result such that the ids are repalced by all of the values in the second table. To visualize the tables I am discussing:
TABLE_USERS
===========
id username group
-- -------- -----
1 jim A
2 alice A
3 brandon B
TABLE_GROUPS
============
id groupname members
-- --------- -------
A designer 134
B photographer 39
DESIRED_SELECTION
=================
id username group
-- -------- -----
1 jim designer
2 alice designer
3 brandon photographer
Thanks!
You do, in fact, want to JOIN the two tables:
SELECT * FROM
TABLE_USERS LEFT JOIN TABLE_GROUPS
ON TABLE_USERS.group = TABLE_GROUPS.id
The trick of joining tables is to find the values that must match in the two tables, and use the on to tell SQL to match them. This table has a ID column to let you do that = you will join the table, ON, and then list the values that need to be equal.
If you do not want all of the columns in both tables, you can simply list only the columns you need in your final query. This means that instead of Select *, you list the columns you want. As shown below, if a column appears with the same name in both tables, you need to prepend the table name, so that SQL know which value you want.
SELECT TABLE_USERS.ID, Username, Groupname
FROM TABLE_USERS
LEFT JOIN TABLE_GROUPS
ON TABLE_USERS.group = TABLE_GROUPS.id
You want a JOIN:
SELECT
u.id,
username,
groupname
FROM
TABLE_USERS AS u
LEFT JOIN TABLE_GROUPS AS g
ON u.group = g.id