Scenario - I have users who are assigned different restrictions over several items. These restrictions are specified in restriction groups. Sometimes it happens that a user is a part of more than one restriction group. Sometimes, by mistake a user is assigned those restriction groups that have a conflict restriction for a common item. For example, User 123 is a part of restriction group A1 and B1 that have a common item Green Ball wherein restriction group A1 has a restriction that User 123 can access only 3 Green Balls a day while restriction group B1 says that User 123 can access only 2 Green Balls a day, thus leading to a conflict. I have to build a query that will fetch the information in such scenarios where there is a conflict. Every user belongs to a particular region, so the results will be filtered using region ID. My query should output.
UserId, Common Item, Restriction Group Name, Restriction
Tables
user - Id, userregionid
userRestriction - userId, restrictionGroup
restrictions- Item, restrictionGroup, restriction, interval // For example, Green Balls, Group A1, 3 , 1 (means 1 day)
My Effort -
select user.id,
userRestriction.restrictionGroup,
restrictions.Item,
restriction.restriction,
restriction.interval
from user left outer join userRestriction on user.Id = userRestriction.userId
left outer join restrictions on userRestriction.restrictionGroup = restriction.restrictionGroup
where user.useregionid= '12345'
group by userRestriction.userid,
user.id,
userRestriction.restrictionGroup,
restrictions.Item,
restriction.restriction,
restriction.interval,user.userregionid
having count(userRestriction.restrictiongroup)>1
I am getting nothing by running this query. This is not correct as I have data that should get resulted.
In my database, I have UserRestriction Table
UserId | RestrictionGroup
EID-999| A1
EID-888 | B1
EID-999 | C1
In the Restriction table
Item | RestrictionGroup| restriction | interval
GreenBalls| A1 | 1 | 1
Pen | B1 |1 | 7
GreenBalls|C1 |1 |30
The query should output
EID-999 | GreenBalls | A1 | 1 | 1
EID-999 | GreenBalls | C1 | 1 |30
User Table :
Id | userregionid
EID-999 | 12345
EID- 888 | 12345
D-900 | 2322
F-999 | 6767
The query should fetch only those users belonging to the specified userregionid.
I think there are some issues with your query. You can try below query -
select U.id,
UR.restrictionGroup,
R.Item,
R.restriction,
R.interval
from users U
left outer join userRestriction UR on U.Id = UR.userId
left outer join restrictions R on UR.restrictionGroup = R.restrictionGroup
where U.userregionid = 12345
group by U.id,
UR.restrictionGroup,
R.Item,
R.restriction,
R.interval
having count(UR.RestrictionGroup) >= 1
DB Fiddle
Related
I am new to Oracle. I have a table where there are multiple restriction groups that are assigned to users. Every group of user belong to a userregionID.
I have to display a list of userregionID where users are assigned more than 1 restriction group.
My Tables
user - Id, userregionid
userRestriction - userId, restrictionGroup
For example,
User Table
EID-999 | 12345
EID- 888 | 12345
D-900 | 2322
F-943 | 6767
UserRestriction Table
UserId | RestrictionGroup
EID-999| A1
EID-888 | B1
EID-999 | C1
F-943 | Z1
F-943 | X1
So, my output should come like
UserRegionId | Count of Users having restriction Group >1
12345 | 1
6767 | 1
because user EID-999 and F-943 belong to userregionId 12345 and 6767 respectively and they are assigned more than 1 restriction group.
My Effort
I have written a query that displays the list of users having > 1 restrictionGroup within the same userregionID
but I am clueless on how to proceed further and convert this query into a nested query that can only fetch the count and userregionID from the entire database.
My query
select distinct ec.userId, e.userregionid,
count(distinct ec.restrictionGroup) over (partition by ec.userId)
from user e, userRestriction ec
where e.userregionid = '12345' and e.Id= ec.userId
You might not need a nested-query here and a INNER JOIN as below can help you.
select u.userregionid, count(ur.userId)
from userRestriction ur, USR u
where ur.userId=u.id
group by ur.userId , u.userregionid
having count(ur.userId) >1;
PS: A DB-Fiddle here can help you to visualize.
I am trying to write an Oracle SQL query to join two tables that are linked via a link table (by that I mean a table with 2 columns, each a foreign key to the primary tables). A min() function is to be used to limit the results from the left outer join to a single row.
My model consists of "parents" and "nephews". Parents can have 0 or more nephews. Parents can be enabled or disabled. Each nephew has a birthday date. The goal of my query is:
Print a single row for each enabled parent, listing that parent's oldest nephew (ie the one with the min(birthday)).
My problem is illustrated here at sqlfiddle: http://sqlfiddle.com/#!4/9a3be0d/1
I can form a query that lists all of the nephews for the enabled parents, but that is not good enough- I just want one row per parent which includes just the oldest nephew. Forming the where clause to the outer table seems to be my stumbling block.
My tables and sample data:
create table parent (parent_id number primary key, parent_name varchar2(50), enabled int);
create table nephew (nephew_id number primary key, birthday date, nephew_name varchar2(50));
create table parent_nephew_link (parent_id number not null, nephew_id number not null);
parent table:
+----+-------------+---------+
| id | parent_name | enabled |
+----+-------------+---------+
| 1 | Donald | 1 |
+----+-------------+---------+
| 2 | Minnie | 0 |
+----+-------------+---------+
| 3 | Mickey | 1 |
+----+-------------+---------+
nephew table:
+-----------+------------+-------------+
| nephew_id | birthday | nephew_name |
+-----------+------------+-------------+
| 100 | 01/01/2017 | Huey |
+-----------+------------+-------------+
| 101 | 01/01/2016 | Dewey |
+-----------+------------+-------------+
| 102 | 01/01/2015 | Louie |
+-----------+------------+-------------+
| 103 | 01/01/2014 | Morty |
+-----------+------------+-------------+
| 104 | 01/01/2013 | Ferdie |
+-----------+------------+-------------+
parent_nephew_link table:
+-----------+-----------+
| parent_id | nephew_id |
+-----------+-----------+
| 1 | 100 |
+-----------+-----------+
| 1 | 101 |
+-----------+-----------+
| 1 | 102 |
+-----------+-----------+
| 3 | 103 |
+-----------+-----------+
| 3 | 104 |
+-----------+-----------+
My (not correct) query:
-- This query is not right, it returns a row for each nephew
select parent_name, nephew_name
from parent p
left outer join parent_nephew_link pnl
on p.parent_id = pnl.parent_id
left outer join nephew n
on n.nephew_id = pnl.nephew_id
where enabled = 1
-- I wish I could add this clause to restrict the result to the oldest
-- nephew but p.parent_id is not available in sub-selects.
-- You get an ORA-00904 error if you try this:
-- and n.birthday = (select min(birthday) from nephew nested where nested.parent_id = p.parent_id)
My desired output would be:
+-------------+-------------+
| parent_name | nephew_name |
+-------------+-------------+
| Donald | Louie |
+-------------+-------------+
| Mickey | Ferdie |
+-------------+-------------+
Thanks for any advice!
John
markaaronky's suggestion
I tried using markaaronky's suggestion but this sql is also flawed.
-- This query is not right either, it returns the correct data but only for one parent
select * from (
select parent_name, n.nephew_name, n.birthday
from parent p
left outer join parent_nephew_link pnl
on p.parent_id = pnl.parent_id
left outer join nephew n
on n.nephew_id = pnl.nephew_id
where enabled = 1
order by parent_name, n.birthday asc
) where rownum <= 1
Why not:
(1) include the n.birthday from the nephews table in your SELECT statement
(2) add an ORDER BY n.birthday ASC to your query
(3) also modify your select so that it only takes the top row?
I tried to write this out in sqlfiddle for you but it doesn't seem to like table aliases (e.g. it throws an error when I write n.birthday), but I'm sure that's legal in Oracle, even though I'm a SQL Server guy.
Also, if I recall correctly, Oracle doesn't have a SELECT TOP like SQL Server does... you have to do something like "WHERE ROWNUM = 1" instead? Same concept... you're just ordering your results so the oldest nephew is the first row, and you're only taking the first row.
Perhaps an undesired side effect is you WOULD get the birthday along with the names in your results. If that's unacceptable, my apologies. It looked like your question has been sitting unanswered for a while and this solution should at least give you a start.
Lastly, since you don't have a NOT NULL constraint on your birthday column and are doing left outer joins, you might make the query safer by adding AND n.birthday IS NOT NULL
Use:
select parent_name, nephew_name
from parent p
left outer join
(
SELECT pnl.parent_id, n.nephew_name
FROM parent_nephew_link pnl
join nephew n
on n.nephew_id = pnl.nephew_id
AND n.BIRTHDAY = (
SELECT min( BIRTHDAY )
FROM nephew n1
JOIN parent_nephew_link pnl1
ON pnl1.NEPHEW_ID = n1.NEPHEW_ID
WHERE pnl1.PARENT_ID = pnl.PARENT_ID
)
) ppp
on p.parent_id = ppp.parent_id
where p.enabled = 1
Demo: http://sqlfiddle.com/#!4/98758/23
| PARENT_NAME | NEPHEW_NAME |
|-------------|-------------|
| Mickey | Louie |
| Donald | Ferdie |
I have a question on a select using join in codeigniter:
I have 2 tables.
table game
id | id_team1 | id_team2
99 | 1 | 2
table team
id | team
1 | Real
2 | Barcelona
I want to return the team to mount a showdown: Real x Barcelona
My select this as well:
$this->db->select('game.*, team.team AS team_name1, team.team AS team_name2');
$this->db->from('game');
$this->db->join('team', 'team.id = game.id_team1');
This way I can return the team first but not the second team or vice versa, changing the join to jogo.id_team2
I must return the two teams as do my join or have otherwise how can I do?
Thanks!
try this
$this->db->select('game.*, team1.team AS team_name1, team2.team AS team_name2');
$this->db->from('game');
$this->db->join('team as team1', 'team1.id = game.id_team1');
$this->db->join('team as team2', 'team2.id = game.id_team2');
I have the following table called questions in HQL Hibernate:
ID | Name
1 | Bread
2 | Bread
3 | Rise
4 | Rise
I want to select each PRODUT only once and if there are multiple PRODUCT with the same name, select the one of the highest id. So, the expected results:
ID | NAME
3 | Bread
4 | Rise
I use the following query:
from Product AS E group by E.producto
So it selects the first 'Product' it encounters instead of the last one.
Thanks
The syntax is almost identical to SQL:
select max(p.id), p.name from Product p group by p.name
Relevant documentation:
http://docs.jboss.org/hibernate/core/4.3/manual/en-US/html/ch16.html#queryhql-aggregation
http://docs.jboss.org/hibernate/core/4.3/manual/en-US/html/ch16.html#queryhql-grouping
I am using the following LINQ query for my profile page:
var userData = from u in db.Users
.Include("UserSkills.Skill")
.Include("UserIdeas.IdeaThings")
.Include("UserInterests.Interest")
.Include("UserMessengers.Messenger")
.Include("UserFriends.User.UserSkills.Skill")
.Include("UserFriends1.User1.UserSkills.Skill")
.Include("UserFriends.User.UserIdeas")
.Include("UserFriends1.User1.UserIdeas")
where u.UserId == userId
select u;
It has a long object graph and uses many Includes. It is running perfect right now, but when the site has many users, will it impact performance much?
Should I do it in some other way?
A query with includes returns a single result set and the number of includes affect how big data set is transfered from the database server to the web server. Example:
Suppose we have an entity Customer (Id, Name, Address) and an entity Order (Id, CustomerId, Date). Now we want to query a customer with her orders:
var customer = context.Customers
.Include("Orders")
.SingleOrDefault(c => c.Id == 1);
The resulting data set will have the following structure:
Id | Name | Address | OrderId | CustomerId | Date
---------------------------------------------------
1 | A | XYZ | 1 | 1 | 1.1.
1 | A | XYZ | 2 | 1 | 2.1.
It means that Cutomers data are repeated for each Order. Now lets extend the example with another entities - 'OrderLine (Id, OrderId, ProductId, Quantity)andProduct (Id, Name)`. Now we want to query a customer with her orders, order lines and products:
var customer = context.Customers
.Include("Orders.OrderLines.Product")
.SingleOrDefault(c => c.Id == 1);
The resulting data set will have the following structure:
Id | Name | Address | OrderId | CustomerId | Date | OrderLineId | LOrderId | LProductId | Quantity | ProductId | ProductName
------------------------------------------------------------------------------------------------------------------------------
1 | A | XYZ | 1 | 1 | 1.1. | 1 | 1 | 1 | 5 | 1 | AA
1 | A | XYZ | 1 | 1 | 1.1. | 2 | 1 | 2 | 2 | 2 | BB
1 | A | XYZ | 2 | 1 | 2.1. | 3 | 2 | 1 | 4 | 1 | AA
1 | A | XYZ | 2 | 1 | 2.1. | 4 | 2 | 3 | 6 | 3 | CC
As you can see data become quite a lot duplicated. Generaly each include to a reference navigation propery (Product in the example) will add new columns and each include to a collection navigation property (Orders and OrderLines in the example) will add new columns and duplicate already created rows for each row in the included collection.
It means that your example can easily have hundreds of columns and thousands of rows which is a lot of data to transfer. The correct approach is creating performance tests and if the result will not satisfy your expectations, you can modify your query and load navigation properties separately by their own queries or by LoadProperty method.
Example of separate queries:
var customer = context.Customers
.Include("Orders")
.SingleOrDefault(c => c.Id == 1);
var orderLines = context.OrderLines
.Include("Product")
.Where(l => l.Order.Customer.Id == 1)
.ToList();
Example of LoadProperty:
var customer = context.Customers
.SingleOrDefault(c => c.Id == 1);
context.LoadProperty(customer, c => c.Orders);
Also you should always load only data you really need.
Edit: I just created proposal on Data UserVoice to support additional eager loading strategy where eager loaded data would be passed in additional result set (created by separate query within the same database roundtrip). If you find this improvement interesting don't forget to vote for the proposal.
(You can improve performance of many includes by creating 2 or more small data request from data base like below.
According to my experience,Only can give maximum 2 includes per query like below.More than that will give really bad performance.
var userData = from u in db.Users
.Include("UserSkills.Skill")
.Include("UserIdeas.IdeaThings")
.FirstOrDefault();
userData = from u in db.Users
.Include("UserFriends.User.UserSkills.Skill")
.Include("UserFriends1.User1.UserSkills.Skill")
.FirstOrDefault();
Above will bring small data set from database by using more travels to the database.
Yes it will. Avoid using Include if it expands multiple detail rows on a master table row.
I believe EF converts the query into one large join instead of several queries. Therefore, you'll end up duplicating your master table data over every row of the details table.
For example: Master -> Details. Say, master has 100 rows, Details has 5000 rows (50 for each master).
If you lazy-load the details, you return 100 rows (size: master) + 5000 rows (size: details).
If you use .Include("Details"), you return 5000 rows (size: master + details). Essentially, the master portion is duplicated over 50 times.
It multiplies upwards if you include multiple tables.
Check the SQL generated by EF.
I would recommend you to perform load tests and measure the performance of the site under stress. If you are performing complex queries on each request you may consider caching some results.
The result of include may change: it depend by the entity that call the include method.
Like the example proposed from Ladislav Mrnka, suppose that we have an entity
Customer (Id, Name, Address)
that map to this table:
Id | Name | Address
-----------------------
C1 | Paul | XYZ
and an entity Order (Id, CustomerId, Total)
that map to this table:
Id | CustomerId | Total
-----------------------
O1 | C1 | 10.00
O2 | C1 | 13.00
The relation is one Customer to many Orders
Esample 1: Customer => Orders
var customer = context.Customers
.Include("Orders")
.SingleOrDefault(c => c.Id == "C1");
Linq will be translated in a very complex sql query.
In this case the query will produce two record and the informations about the customer will be replicated.
Customer.Id | Customer.Name | Order.Id | Order.Total
-----------------------------------------------------------
C1 | Paul | O1 | 10.00
C1 | Paul | O2 | 13.00
Esample 2: Order => Customer
var order = context.Orders
.Include("Customers")
.SingleOrDefault(c => c.Id == "O1");
Linq will be translated in a simple sql Join.
In this case the query will produce only one record with no duplication of informations:
Order.Id | Order.Total | Customer.Id | Customer.Name
-----------------------------------------------------------
O1 | 10.00 | C1 | Paul