I have a distinct list of part numbers from one table. It is basically a table that contains a record of all the company's part numbers. I want to add columns that will pull data from different tables but only pertaining to the part number on that row of the distinct part list.
For example: if I have part A, B, C from the unique part list I want to add columns for Purchase quantity, repair quantity, loan quantity, etc... from three totally unique tables.
So it's almost like I need 3 subqueries that will sum of that data from the different tables for each part.
Can anybody steer me in the direction of how to do this? Please and thank you so much!
One method is correlated subqueries. Something like this:
select p.*,
(select count(*)
from purchases pu
where pu.part_id = p.part_id
) as num_purchases,
(select count(*)
from repairs r
where r.part_id = p.part_id
) as num_repairs,
(select count(*)
from loans l
where l.part_id = p.part_id
) as num_loans
from parts p;
Another option is joins with aggregation before the join. Or lateral joins (which are quite similar to correlated subqueries).
Related
Overall what I'm trying to achieve is a query that shows the most ordered item from a customer in a database. To achieve this I've tried making a query showing how many times a customer has ordered an item, and now I am trying to create a sub-query in it using TOP1 to discern the most bought items.
With the SQL from the first query (looking weird because I made it with the Access automatic creator):
SELECT
Customers.CustomerFirstName,
Customers.CustomerLastName,
Products.ProductName,
COUNT(SalesQuantity.ProductCode) AS CountOfProductCode
FROM (Employees
INNER JOIN (Customers
INNER JOIN Sales
ON Customers.CustomerCode = Sales.CustomerCode)
ON Employees.EmployeeCode = Sales.EmployeeCode)
INNER JOIN (Products
INNER JOIN SalesQuantity
ON Products.ProductCode = SalesQuantity.ProductCode)
ON Sales.SalesCode = SalesQuantity.SalesCode
GROUP BY
Customers.CustomerFirstName,
Customers.CustomerLastName,
Products.ProductName
ORDER BY
COUNT(SalesQuantity.ProductCode) DESC;
I have tried putting in a subquery after FROM line:
(SELECT TOP1 CountOfProduct(s)
FROM (.....)
ORDER by Count(SalesQuantity.ProductCode) DESC)
I'm just not sure what to put in for the "from"-every other tutorial has the data from an already created table, however this is from a query that is being made at the same time. Just messing around I've put "FROM" and then listed every table, as well as
FROM Count(SalesQuantity.ProductCode)
just because I've seen that in the order by from the other code, and assume that the query is discerning from this count. Both tries have ended with an error in the syntax of the "FROM" line.
I'm new to SQL so sorry if it's blatantly obvious, but any help would be greatly appreciated.
Thanks
As I understand, you want the most purchased product for each customer.
So, begin by building aggregate query that counts product purchases by customer (appears to be done in the posted image). Including customer ID in the query would simplify the next step which is to build another query with TOP N nested query.
Part of what complicates this is unique record identifier is lost because of aggregation. Have to use other fields from the aggregate query to provide unique identifier. Consider:
SELECT * FROM Query1 WHERE CustomerID & ProductName IN
(SELECT TOP 1 CustomerID & ProductName FROM Query1 AS Dupe
WHERE Dupe.CustomerID = Query1.CustomerID
ORDER BY Dupe.CustomerID, Dupe.CountOfProductCode DESC);
Overall what I'm trying to achieve is a query that shows the most ordered item from a customer in a database.
This answers your question. It does not modify your query which is only tangentially related.
SELECT s.CustomerCode, sq.ProductCode, SUM(sq.quantity) as qty
FROM Sales as s INNER JOIN
SalesQuantity as sq
ON s.SalesCode = sq.SalesCode
GROUP BY s.CustomerCode, sq.ProductCode;
To get the most ordered items, you can use this twice:
SELECT s.CustomerCode, sq.ProductCode, SUM(sq.quantity) as qty
FROM Sales as s INNER JOIN
SalesQuantity as sq
ON s.SalesCode = sq.SalesCode
GROUP BY s.CustomerCode, sq.ProductCode
HAVING sq.ProductCode IN (SELECT TOP 1 sq2.ProductCode
FROM Sales as s2 INNER JOIN
SalesQuantity as sq2
ON s2.SalesCode = sq2.SalesCode
WHERE s2.CustomerCode = s.CustomerCode
GROUP BY sq2.ProductCode
);
In almost any other database, this would be simpler, because you would be able to use window functions.
Hi I’m trying to write a query and I’m struggling to figure out how to go about it.
I have a suppliers table and a supplier parts table I want to write a query that lists suppliers that have specified related Parts in the supplier parts table. If a supplier doesn’t have all specified related parts then they should not be listed.
At the moment I have written a very basic query that lists the supplier if they have a related supplier part that meets the criteria.
SELECT id ,name
FROM
efacdb.dbo.suppliers INNER JOIN [efacdb].[dbo].[spmatrix] ON
id = spmsupp
WHERE spmpart
IN ('ALUM_5083', 'ALUM_6082')
I only want to show the supplier if they have both parts related. Does anyone know how I could do this?
Use a subquery with counting distinct occurences:
select * from suppliers s
where 2 = (select count(distinct spmpart) from spmatrix
where id = spmsupp and spmpart in ('ALUM_5083', 'ALUM_6082'))
As a note, you can modify your query to get what you want, just by using an aggregation:
SELECT id, name
FROM efacdb.dbo.suppliers INNER JOIN
[efacdb].[dbo].[spmatrix]
ON id = spmsupp
WHERE spmpart IN ('ALUM_5083', 'ALUM_6082')
GROUP BY id, name
HAVING MIN(spmpart) <> MAX(spmpart);
If you know there are no duplicates, then having count(*) = 2 also solves the problem.
I'm relatively new to sql so this may probably come off as a simple questions.
I have 3 tables A,B,C
B has a FK to A, and C has a FK to B
I would like to get all the distinct entries in A that has an entry in B that corresponds to an entry in C. With JOINs I currently have:
SELECT DISTINCT *
FROM Peoples p
INNER JOIN Contracts c
ON p.pkey=c.person_pkey
JOIN audits a ON c.contract_pkey=a.contract_issued_for;
So this returns the list of all people (with duplicates) with an audit. How do I get it so that instead of return columns of all the tables put together, but rather just all the columns that belong to table peoples and are unique entries?
Thanks in advance!
Replace
SELECT DISTINCT *
with
SELECT DISTINCT p.*
SELECT DISTINCT p.*
FROM Peoples p
...
The minimal change to your query would be to change * to p.*. However, I think a better approach is to use IN clauses rather than JOINs:
SELECT *
FROM Peoples
WHERE pkey IN
( SELECT person_pkey
FROM Contracts
WHERE contract_pkey IN
( SELECT contract_issued_for
FROM audits
)
)
;
This makes clear what the query is really doing: it's finding people who have contracts that audits have been issued for, and is not otherwise interested in those contracts or audits.
I'm taking a database course this semester, and we're learning SQL. I understand most simple queries, but I'm having some difficulty using the count aggregate function.
I'm supposed to relate an advertisement number to a property number to a branch number so that I can tally up the amount of advertisements by branch number and compute their cost. I set up what I think are two appropriate new views, but I'm clueless as to what to write for the select statement. Am I approaching this the correct way? I have a feeling I'm over complicating this bigtime...
with ad_prop(ad_no, property_no, overseen_by) as
(select a.ad_no, a.property_no, p.overseen_by
from advertisement as a, property as p
where a.property_no = p.property_no)
with prop_branch(property_no, overseen_by, allocated_to) as
(select p.property_no, p.overseen_by, s.allocated_to
from property as p, staff as s
where p.overseen_by = s.staff_no)
select distinct pb.allocated_to as branch_no, count( ??? ) * 100 as ad_cost
from prop_branch as pb, ad_prop as ap
where ap.property_no = pb.property_no
group by branch_no;
Any insight would be greatly appreciated!
You could simplify it like this:
advertisement
- ad_no
- property_no
property
- property_no
- overseen_by
staff
- staff_no
- allocated_to
SELECT s.allocated_to AS branch, COUNT(*) as num_ads, COUNT(*)*100 as ad_cost
FROM advertisement AS a
INNER JOIN property AS p ON a.property_no = p.property_no
INNER JOIN staff AS s ON p.overseen_by = s.staff_no
GROUP BY s.allocated_to;
Update: changed above to match your schema needs
You can condense your WITH clauses into a single statement. Then, the piece I think you are missing is that columns referenced in the column definition have to be aggregated if they aren't included in the GROUP BY clause. So you GROUP BY your distinct column then apply your aggregation and math in your column definitions.
SELECT
s.allocated_to AS branch_no
,COUNT(a.ad_no) AS ad_count
,(ad_count * 100) AS ad_cost
...
GROUP BY s.allocated_to
i can tell you that you are making it way too complicated. It should be a select statement with a couple of joins. You should re-read the chapter on joins or take a look at the following link
http://www.sql-tutorial.net/SQL-JOIN.asp
A join allows you to "combine" the data from two tables based on a common key between the two tables (you can chain more tables together with more joins). Once you have this "joined" table, you can pretend that it is really one table (aliases are used to indicate where that column came from). You understand how aggregates work on a single table right?
I'd prefer not to give you the answer so that you can actually learn :)
Of all the thousands of queries I've written, I can probably count on one hand the number of times I've used a non-equijoin. e.g.:
SELECT * FROM tbl1 INNER JOIN tbl2 ON tbl1.date > tbl2.date
And most of those instances were probably better solved using another method. Are there any good/clever real-world uses for non-equijoins that you've come across?
Bitmasks come to mind. In one of my jobs, we had permissions for a particular user or group on an "object" (usually corresponding to a form or class in the code) stored in the database. Rather than including a row or column for each particular permission (read, write, read others, write others, etc.), we would typically assign a bit value to each one. From there, we could then join using bitwise operators to get objects with a particular permission.
How about for checking for overlaps?
select ...
from employee_assignments ea1
, employee_assignments ea2
where ea1.emp_id = ea2.emp_id
and ea1.end_date >= ea2.start_date
and ea1.start_date <= ea1.start_date
Whole-day inetervals in date_time fields:
date_time_field >= begin_date and date_time_field < end_date_plus_1
Just found another interesting use of an unequal join on the MCTS 70-433 (SQL Server 2008 Database Development) Training Kit book. Verbatim below.
By combining derived tables with unequal joins, you can calculate a variety of cumulative aggregates. The following query returns a running aggregate of orders for each salesperson (my note - with reference to the ubiquitous AdventureWorks sample db):
select
SH3.SalesPersonID,
SH3.OrderDate,
SH3.DailyTotal,
SUM(SH4.DailyTotal) RunningTotal
from
(select SH1.SalesPersonID, SH1.OrderDate, SUM(SH1.TotalDue) DailyTotal
from Sales.SalesOrderHeader SH1
where SH1.SalesPersonID IS NOT NULL
group by SH1.SalesPersonID, SH1.OrderDate) SH3
join
(select SH1.SalesPersonID, SH1.OrderDate, SUM(SH1.TotalDue) DailyTotal
from Sales.SalesOrderHeader SH1
where SH1.SalesPersonID IS NOT NULL
group by SH1.SalesPersonID, SH1.OrderDate) SH4
on SH3.SalesPersonID = SH4.SalesPersonID AND SH3.OrderDate >= SH4.OrderDate
group by SH3.SalesPersonID, SH3.OrderDate, SH3.DailyTotal
order by SH3.SalesPersonID, SH3.OrderDate
The derived tables are used to combine all orders for salespeople who have more than one order on a single day. The join on SalesPersonID ensures that you are accumulating rows for only a single salesperson. The unequal join allows the aggregate to consider only the rows for a salesperson where the order date is earlier than the order date currently being considered within the result set.
In this particular example, the unequal join is creating a "sliding window" kind of sum on the daily total column in SH4.
Dublicates;
SELECT
*
FROM
table a, (
SELECT
id,
min(rowid)
FROM
table
GROUP BY
id
) b
WHERE
a.id = b.id
and a.rowid > b.rowid;
If you wanted to get all of the products to offer to a customer and don't want to offer them products that they already have:
SELECT
C.customer_id,
P.product_id
FROM
Customers C
INNER JOIN Products P ON
P.product_id NOT IN
(
SELECT
O.product_id
FROM
Orders O
WHERE
O.customer_id = C.customer_id
)
Most often though, when I use a non-equijoin it's because I'm doing some kind of manual fix to data. For example, the business tells me that a person in a user table should be given all access roles that they don't already have, etc.
If you want to do a dirty join of two not really related tables, you can join with a <>.
For example, you could have a Product table and a Customer table. Hypothetically, if you want to show a list of every product with every customer, you could do somthing like this:
SELECT *
FROM Product p
JOIN Customer c on p.SKU <> c.SSN
It can be useful. Be careful, though, because it can create ginormous result sets.