I am new at access SQL and i need help with some query. What i want is to find those customers that prefer a car (manufacturer and model) from prefer_to_buy AND prefer_to_rent that no one else prefer.
For example if 2 customers prefer toyota aygo must not be in the result table.
customer(customer_id,name)
prefer_to_buy(customer_id,manufacturer,model)
prefer_to_rent(customer_id, manufacturer,model)
I have tried a lot of ways including exists and i know there must be about 2-3 subqueries but i cant get it to work, any ideas?
Your problem definition is very vague, so the answer is also sort of generic. You should try to create a Left Outer Join on customer table and, for example, a "prefer_to_buy" Table using customer_id as a join field, and include:
customer_id,name from the left table and manufacturer,model from the right table. The same logic applies to prefer_to_rent Table: you can actually combine these 3 Tables in a single Access SQL query using the aforementioned Outer Joins.
Hope this may help. Best regards,enter code here
There are a couple of parts to cover here. First, you could use the union operator to treat prefer_to_buy and prefer_to_rent as a single table (possibly with an additional literal "column" to indicate preference type). Once you've done this, you could use the exists operator to make sure no other customers prefer this car:
SELECT c.name, p.manufacturer, p.model
FROM customer c
JOIN (SELECT customer_id, manufacturer, model
FROM prefer_to_buy
UNION
SELECT customer_id, manufacturer, model
FROM prefer_to_buy) p ON c.customer_id = p.customer_id
WHERE NOT EXISTS (SELECT *
FROM prefer_to_buy pb
WHERE c.customer_id != pb.customer_id AND
p.manufacturer = pb.manufacturer AND
p.model = pb.model) AND
NOT EXISTS (SELECT *
FROM prefer_to_rent pr
WHERE c.customer_id != pr.customer_id AND
p.manufacturer = pr.manufacturer AND
p.model = pr.model)
First you need to do to two joins one on prefer_to_buy AND one on prefer_to_rent.
Next, you need to check if any one else would like the same manufacturer and model. Do this with a exist
SELECT *
FROM customer AS c
JOIN prefer_to_buy AS pb ON c.customer_id = pb.customer_id
JOIN prefer_rent AS pr ON c.customer_id = pr.customer_id
WHERE NOT EXISTS ( SELECT 'x' FROM prefer_to_buy AS pb1 WHERE pb.manufacturer = pb1.manufacturer AND pb.model = pb1.model AND pb.customer_id <> pb1.customer_id)
AND NOT EXISTS ( SELECT 'x' FROM prefer_to_rent AS pr1 WHERE pb.manufacturer = pr1.manufacturer AND pb.model = pr1.model AND pb.customer_id <> pr1.customer_id)
Related
I have two tables, CustomerCost and Products that look like the following:
I am joining the two tables using the following SQL query:
SELECT custCost.ProductId,
custCost.CustomerCost
FROM CUSTOMERCOST Cost
LEFT JOIN PRODUCTS prod ON Cost.productId =prod.productId
WHERE prod.productId=4
AND (Cost.Customer_Id =2717
OR Cost.Customer_Id IS NULL)
The result of the join is:
joins result
What i want to do is when I pass customerId 2717 it should return only specific customer cost i.e. 258.93, and when customerId does not match then only it should take cost as 312.50
What am I doing wrong here?
You can get your expected output as follows:
SELECT Cost.ProductId,
Cost.CustomerCost
FROM CUSTOMERCOST Cost
INNER JOIN PRODUCTS prod ON Cost.productId = prod.productId
WHERE prod.productId=4
AND Cost.Customer_Id = 2717
However, if you want to allow customer ID to be passed as NULL, you will have to change the last line to AND Cost.Customer_Id IS NULL. To do so dynamically, you'll need to use variables and generate the query based on the input.
The problem in the original query that you have posted is that you have used an alias called custCost which is not present in the query.
EDIT: Actually, you don't even need a join. The CUSTOMERCOST table seems to have both Customer and Product IDs.
You can simply:
SELECT
Cost.ProductId, Cost.CustomerCost
FROM
CUSTOMERCOST Cost
WHERE
Cost.Customer_Id = 2717
AND Cost.productId = 4
You seem to want:
SELECT c.*
FROM CUSTOMERCOST c
WHERE c.productId = 4 AND c.Customer_Id = 2717
UNION ALL
SELECT c.*
FROM CUSTOMERCOST c
WHERE c.productId = 4 AND c.Customer_Id IS NULL AND
NOT EXISTS (SELECT 1 FROM CUSTOMERCOST c2 WHERE c2.productId = 4 AND c2.Customer_Id = 2717);
That is, take the matching cost, if it exists for the customer. Otherwise, take the default cost.
SELECT custCost.ProductId,
custCost.CustomerCost
FROM CUSTOMERCOST Cost
LEFT JOIN PRODUCTS prod
ON Cost.productId =prod.productId
AND (Cost.Customer_Id =2717 OR Cost.Customer_Id IS NULL)
WHERE prod.productId=4
WHERE applies to the joined row. ON controls the join condition.
Outer joins are why FROM and ON were added to SQL-92. The old SQL-89
syntax had no support for them, and different vendors added different,
incompatible syntax to support them.
I have these 3 tables:
product table
id
siteId
optionsSet table
id
productId
...
option table
id
optionsSetId
code
...
Question:
How can I make a SQL query to select all from option table by knowing these two: option.code and product.siteId ?
I know how to do a query with JOIN on two tables, but I am struggling with joining these three tables.
Something like
SELECT
*
FROM
option
WHERE
code = #code
AND optionsSetId IN
(SELECT
os.id
FROM
optionsSet os
JOIN product p ON os.productId = p.Id
WHERE
p.siteId = #siteId)
where #code is your code parameter and #siteId is your siteid parameter
to use inner joins you would have to join all 3 tables together and that would like
SELECT
DISTINCT o.*
FROM
option o
JOIN optionsSet os ON o.optionsSetId = os.Id
JOIN product p ON os.productId = p.Id
WHERE
o.code = #code
AND p.siteId = #site
if you notice that requires a DISTINCT to only get the data from option. It may be simpler and easier to understand but not very efficient.
another option that someone will probably say is way more awesome is using EXISTS
SELECT
o.*
FROM
OPTION o
WHERE
o.code = #code
AND EXISTS(
SELECT
1
FROM
optionsSet os
JOIN product p ON os.productId = p.Id
WHERE
o.optionSetId = os.Id
AND p.siteId = #siteId
)
I used EXISTS exclusively for a few years and the started working on databases with tables that had +100million records and IN was faster than EXISTS in some cases and identical in the others. Plus IN is less code.
SELECT * FROM option
LEFT JOIN product
ON option.code = product.siteId (+)
--(+) is a left outter join. This should include all of the values in option.code and all of the values in product that have the same siteId as values in option.
I'm unsure on how you want OptionSet to relate to the other 2 databases though?
if you want to include the third tables result you can just add another join on that table for the condition you want.
This is working fine
SELECT i.*,o.*,p.*
FROM orders o
INNER JOIN oitems i
ON i.orderid = o.orderid
LEFT OUTER JOIN products p
ON i.catalogid = p.catalogid
however i want to perform a nested select as an example this is giving the coulmn x exists more than once
SELECT AA.*,
FROM (
SELECT i.*,o.*,p.*
FROM orders o
INNER JOIN oitems i
ON i.orderid = o.orderid
LEFT OUTER JOIN products p
ON i.catalogid = p.catalogid ) AA
i know the second example makes no sense , but i need another select with groupping, is there a way to fix the coulm exists more than once error without having to specify the column names in the select statement?
By using *, you are getting the same column more than once in your output. To avoid, this, specifically state the columns you want returned, instead.
The culprits are likely orderid and catalogid which both exist in more than one table, but there may be others.
You have mention column names specifically. I can see that you are using "*". you have to use like select i.columnName,o.columnName etc
Hi all I have a problem with an SQL query: the problem is that if i add GROUP BY the database engine outputs the error:
Column 'dbo.classes.class_name' is invalid in the select list because
it is not contained in either an aggregate function or the GROUP BY clause.
My query is:
string query = "SELECT p.*
FROM dbo.classes AS p INNER JOIN teacher_classes AS a
ON a.class_id = p.class_id
and teach_id = #id
GROUP BY p.class_id";
Is there any help please for that.
Note without group by the query work fine but the result not grouped.
Your query is:
SELECT p.*
FROM dbo.classes AS p INNER JOIN
teacher_classes AS a
ON a.class_id = p.class_id and teach_id = #id
GROUP BY p.class_name;
You are trying to select all the columns from p and yet you're are grouping by class_name. This is not allowed in most databases. What happens if you have two classes, but information is different from them?
One option is to use distinct rather than group by to remove duplicates:
SELECT distinct c.*
FROM dbo.classes c INNER JOIN
teacher_classes tc
ON tc.class_id = c.class_id and tc.teach_id = #id;
Another option is to use something like in to find the matching classes for the teacher:
select c.*
from classes c
where c.class_id in (select tc.class_id from teacher_classes where teach_id = #id)
Notice I also changed your aliases so they have some relationship to the table names. This makes the query much easier to read.
I'm working with a moderately large MSAccess .mdb file that I need to manipulate with SQL. Unfortunately some statements which work in theory seem to cause it to hang, and I've run into a brick wall.
Here is a simplified representation in SQL Fiddle
Three tables: products, product_category, and categories
I need to SELECT categories that ONLY contain items that have the field 'HIDE = 1'
If a category contains products that are hide = 0, it should not be selected.
I can do this relatively easily with subqueries, but the query stalls out. In the past queries that rely on left joins seem to execute efficiently, but I cannot wrap my mind around joins enough to translate this query into that format.
EDIT:
SELECT c.categoryid
FROM product_category AS c
LEFT JOIN
(
SELECT DISTINCT c.categoryid
FROM product_category AS c
LEFT JOIN products AS p
ON c.catalogid = p.catalogid
WHERE p.hide = 0
) y ON y.categoryid = c.categoryid
WHERE y.categoryid IS NULL
Someone posted the above query as an answer but then for some reason deleted it. As far as I can tell it works and works quickly. I consider this question to be answered. If I remember I will self-post the answer once the timer allows me to.
I believe you just need to un-correlate the subquery eg...
SELECT c.categoryid FROM product_category AS c
WHERE c.categoryid NOT IN
(SELECT DISTINCT c1.categoryid FROM product_category AS c1
LEFT JOIN products AS p ON c1.catalogid = p.catalogid
WHERE p.hide = 0)
Note how I have aliased the subquery product_category table as c1 instead of c - This means the subquery will only execute once as opposed to once for every row of the your main query.
SQL Fiddle
Note that there will no doubt be more efficiencies still to be found however I think this will suffice for your purposes.
In fact there is no need for a LEFT JOIN here I don't think ie...
SELECT c.categoryid FROM product_category AS c
WHERE c.categoryid NOT IN
(SELECT DISTINCT c1.categoryid FROM product_category AS c1
INNER JOIN products AS p ON c1.catalogid = p.catalogid
WHERE p.hide = 0)
..This will afford you some extra speed.
If there is only one categoryid per catalogid then you can get rid of the distinct:
Select
c.id, c.categoryname
From
category c
Where
Not Exists (
Select
'x'
From
products p
Inner Join
product_category pc
on pc.catalogid = p.catalogid
Where
pc.categoryid = c.id and
p.hide = 0
)
Edited - the test data in the fiddle seems wrong, I've corrected it. This should work now
http://sqlfiddle.com/#!6/56f5e/1/0