Hi were trying to perform a mysql select which isnt going to plan and hoping someone can shed some light on it.
we have estimated 10,000 plus listing records, a customer can have several listing records for different locations. we need to select all customer listings where at least one of the locations is equal to a specifield location.
so for example lets say customer 1 has a listing in sheffiled, doncaster, leeds, wakefield and customer 2 has listings in london and brighton.
Now I want to select all customer listings where one of the listings is for the area sheffield.
Id hope to get back the 4 rows for customer 1 because one of his listings is in sheffield.
for the sake of this example lets just presume the table consists of just customerId and LocationName
I need to select all customerIds where one of the locationNames = sheffield. So Id get 4 rows retruend with the cusotmer ID and the 4 locations
How do you write this query in mysql? Im guessing subselect but not too sure.
SELECT customerid FROM customers_location
WHERE customerid IN(SELECT DISTINCT customerid FROM customers_location WHERE LocationName = 'sheffield')
Something like:
SELECT * FROM CUST_TABLE WHERE CUST_ID IN (
SELECT DISTINCT CUST_ID FROM CUST_TABLE WHERE CUST_LOCN='Sheffield')
Note; The distinct clause may not be strictly necessary, not sure.
That would give you eg. 4 records for customer xyz who has one of their listing locations as Sheffield, which I think is what you're asking.
Related
I have a access table that has quarterly pricing data starting from 20100131 and goes on as 20100430, 20100731.... 20170131, 20170430. For each pricing date, there are many loans. Some loans stay in the portfolio, some loans are removed and some added for each pricing period. I would like to find the list of loans that exist in all periods and see their price for each period. So i have the "Loan_Number" field and "Price_Date" field. I would like to find the Loan Numbers that exist in all price date points. I appreciate the help.
Thanks!
Would have been nice to see some effort from you but I was intrigued with the challenge so here is what I accomplished.
1 - Need a dataset of all possible combinations of loan numbers and date values. So if you have a LoanNumbers table and a Periods table, create a Cartesian query called AllPairs:
SELECT LoanNumbers.Loan_Number, Periods.Price_Date FROM LoanNumbers, Periods;
If you don't have those tables, generate datasets with queries, assuming the data table has at least one record for every loan number and at least one record for every period:
SELECT DISTINCT Table1.Price_Date FROM Table1;
SELECT DISTINCT Table1.Loan_Number FROM Table1;
2 - Join AllPairs to data table for a 'find unmatched' query called LoanNoPeriod:
SELECT AllPairs.Loan_Number, AllPairs.Price_Date, Table1.Loan_Number, Table1.Price_Date
FROM AllPairs LEFT JOIN Table1 ON (AllPairs.Price_Date = Table1.Price_Date) AND (AllPairs.Loan_Number = Table1.Loan_Number)
WHERE (((Table1.Price_Date) Is Null));
3 - Final query:
SELECT * FROM Table1 WHERE Loan_Number NOT IN (SELECT AllPairs.Loan_Number FROM LoanNoPeriod);
Be aware these type of queries can perform very slowly and with very large datasets might not be practical.
We want to select customers based on following parameters i.e. customer should be in:
specific city i.e. cityId=1,2,3...
specific customerId should be excluded i.e. customerId=33,2323,34534...
specific age i.e. 5 years, 7 years, 72 years...
This inclusion & exclusion list can be any long.
How should we design database for this:
Create separate table 'customerInclusionCities' for these inclusion cities and do like:
select * from customers where cityId in (select cityId from customerInclusionCities)
Some we do for age, create table 'customerEligibleAge' with all entries of eligible age entries:
i.e. select * from customers where age in (select age from customerEligibleAge)
and Create separate table 'customerIdToBeExcluded' for excluding customers:
i.e. select * from customers where customerId not in (select customerId from customerIdToBeExcluded)
OR
Create One table with Category and Ids.
i.e. Category1 for cities, Category2 for CustomerIds to be excluded.
Which approach is better, creating one table for these parameters OR creating separate tables for each list i.e. age, customerId, city?
IN ( SELECT ... ) can be very slow. Do your query as a single SELECT without subqueries. I assume all 3 columns are in the same table? (If not, that adds complexity.) The WHERE clause will probably have 3 IN ( constants ) clauses:
SELECT ...
FROM tbl
WHERE cityId IN (1,2,3...)
AND customerId NOT IN (33,2323,34534...)
AND age IN (5, 7, 72)
Have (at least):
INDEX(cityId),
INDEX(age)
(Negated things are unlikely to be able to use an index.)
The query will use one of the indexes; having both will give the Optimizer a choice of which it thinks is better.
Or...
SELECT c.*
FROM customers AS c
JOIN cityEligible AS b ON b.city = c.city
JOIN customerEligibleAge AS ce ON c.age = ce.age
LEFT JOIN customerIdToBeExcluded AS ex ON c.customerId = ex.customerId
WHERE ex.customerId IS NULL
Suggested indexes (probably as PRIMARY KEY):
customers: (city)
customerEligibleAge: (age)
customerIdToBeExcluded: (customerId)
In order to discuss further, please provide SHOW CREATE TABLE for each table and EXPLAIN SELECT ... for any of the queries actually work.
If you use the database only that operation, I recommend to use the first solution. Also the first solution is very simple to deploy.
The second solution fills up with junk the DB.
I have two tables. One is a category ID, the other one is a product table. I would like to count how many products of each category ID, and the query is below.
SELECT hkgg_emall_goods_class.gc_id, COUNT(*) as productcount
FROM hkgg_emall_goods_class
LEFT JOIN hkgg_emall_goods
ON hkgg_emall_goods.gc_id=hkgg_emall_goods_class.gc_id GROUP BY hkgg_emall_goods_class.gc_id ;
It shows what I want, except the query shows some rows to have count of 1 even they have no products associated, and some row as 1 count when they actually have one product associated.
I want your advice on
1) how to solve this problem
2) I have added the gc_productcount column in the category table. How can I insert the count query into the gc_productcount column for every row?
INSERT INTO `hkgg_emall_goods_class.gc_productcount`
This query is not working well when I put it in front of the select count query.
P.S. I have browsed the other thread in stackoverflow, but luck is not good enough to browse a similar solution.
Thank you in advance.
Assuming hkgg_emall_goods table has a primary or at least a unique key, that's what you want to count. i.e. you don't want to COUNT(*), you want to COUNT(hkgg_emall_goods.id).
So assuming that primary key is hkgg_emall_goods.id then your query will look like this:
SELECT
hgc.gc_id,
COUNT(hg.id) AS productcount
FROM hkgg_emall_goods_class hgc
LEFT JOIN hkgg_emall_goods hg ON hg.gc_id = hgc.gc_id
GROUP BY
hgc.gc_id
I have an SQL table data as follow
I want to display single record for product
example
90792 Amlaan-Hi-Power .............. Show only 1 record when there are 2 record
90793 Amlaan-Neutral .............. show only 1 record when there are 2 record
90794 Amlaan-Phosphate free .........show only 1 record when there are 2 record
90801 Acetone .......................show only 1 record when there are 2 record
90901 Acetanilide ...................show only 1 record when there is 1 record
Can I do this using Inner join
I know
select distinct product from product ORDER BY `product`.`product` DESC
will select distinct (unique) product code and that to only one field i.e. product but confused how to get other information using SQL statement
but results in duplicate records or same table...........................
It looks like your duplicate rows vary by the quantity of product in the package.
You can display just the product and name with
SELECT DISTINCT product, name
FROM product
If you want to deal with the quantity as well, that's a little trickier. This might work: it will put all product codes on one line.
SELECT product,
GROUP_CONCAT(product_code ORDER BY product_code) product_codes,
name
FROM product
GROUP BY product, name
Self join doesn't make a whole lot of sense for this application.
Use group by option for such purposes.
SELECT product,GROUP_CONCAT(product_code SEPERATOR '|') AS product_code,name FROM Table GROUP BY NAME
It will show only one record for duplicate names.
The multiple enteries of product code will seperated by | .
I am fairly new to Databases and I am just beginning to understand the DML/queries, I have two tables, one named customer this contain customer data and one named requested_games, this contains games requested by the customers, I would like to write a query that will return the customers that have requested more than two games, so far when I run the query, I don't get the desired result, not sure if I'm doing it right.
Can anyone assist with this thanks,
Below is a snippet of the query
select customers.customer_name, wants_list.requested_game, wants_list.wantslists_id,count(wants_list.customers_ID)
from customers, wants_list
where customers.customers_ID = wants_list.customers_id
and wants_list.wantslists_id = wants_list.wantslists_id
and wants_list.requested_game > '2';
just include a HAVING clause
GROUP BY customers_ID
HAVING COUNT(*) > 2
depending on how you have your data setup you may need to do
HAVING COUNT(wants_list.requested_game) > 2
This is how I like to describe how a query works maybe itll help you visualize how the query executes :)
SELECT is making an order at a restaurant....
FROM is the menu you want to order from....
JOIN is what sections of the menu you want to include
WHERE is any customization you want to make to your order (aka no mushrooms)....
GROUP BY (and anything after) is after the order has been completed and is at your table...
GROUP BY tells your server to bring your types of food together in groups
ORDER BY is saying what dishes you want first (aka i want my entree then dessert then appetizer ).
HAVING can be used to pick out any mushrooms that were accidentally left on the plate....
etc..
I would like to write a query that will return the customers that
have requested more than two games
For this to happen you need to do the following
First you need to use GROUP BY to group the games based on customers (customers_id)
Then you need to use HAVING clause to get customers who requested more than two games
Then make this a SUBQUERY if you need more information on the customer like name
Finally you use a JOIN between customers and the sub query (temp) to display more information on the customer
Like the following query
SELECT customers.customer_id, customers.customer_name, game_count
FROM (SELECT customer_id, count(wantslists_id) AS game_count
FROM wants_list
GROUP BY customer_id
HAVING count(requested_game) > '2') temp
JOIN customers ON customers.customer_id = temp.customer_id