Basically, I want to get all rows from the customers table that do NOT appear in the brochure_requests table.
SELECT *
FROM customers JOIN brochure_requests
WHERE brochure_requests.first_name != customers.customer_first_name
AND brochure_requests.last_name != customers.customer_last_name
The query works when the parameters are =, but as soon as I run a != query, the program (HeidiSQL) hangs indefinitely or until I cancel it.
don't you have a customerID in the brochure_requests table?
If you do, you can do something like this:
select * from customers
where customerId not in (select customerId from brochure_requests)
Use NOT EXISTS, e.g.
SELECT *
FROM customers
WHERE NOT EXISTS (
SELECT 1
FROM brochure_requests
WHERE brochure_requests.first_name = customers.customer_first_name
AND brochure_requests.last_name = customers.customer_last_name)
I would also suggest adding an index on the brochure_requests.first_name and brochure_requests.last_name fields for improved performance.
SELECT
*
FROM
customers
LEFT JOIN brochure_requests
ON brochure_requests.first_name = customers.customer_first_name
AND brochure_requests.last_name = customers.customer_last_name
WHERE
brochure_requests.first_name IS NULL
Also, consider normalising your database by adding CustomerID to brochure_requests as a foreign key instead of duplicating the first and last names.
Related
i have following sql in java project:
select distinct * from drivers inner join licenses on drivers.user_id=licenses.issuer_id
inner join users on drivers.user_id=users.id
where (licenses.state='ISSUED' or drivers.status='WAITING')
and users.is_deleted=false
And result i database looks like this:
And i would like to get only one result instead of two duplicated results.
How can i do that?
Solution 1 - That's Because one of data has duplicate value write distinct keyword with only column you want like this
Select distinct id, distinct creation_date, distinct modification_date from
YourTable
Solution 2 - apply distinct only on ID and once you get id you can get all data using in query
select * from yourtable where id in (select distinct id from drivers inner join
licenses
on drivers.user_id=licenses.issuer_id
inner join users on drivers.user_id=users.id
where (licenses.state='ISSUED' or drivers.status='WAITING')
and users.is_deleted=false )
Enum fields name on select, using COALESCE for fields which value is null.
usually you dont query distinct with * (all columns), because it means if one column has the same value but the rest isn't, it will be treated as a different rows. so you have to distinct only the column you want to, then get the data
I suspect that you want left joins like this:
select *
from users u left join
drivers d
on d.user_id = u.id and d.status = 'WAITING' left join
licenses l
on d.user_id = l.issuer_id and l.state = 'ISSUED'
where u.is_deleted = false and
(d.user_id is not null or l.issuer_id is not null);
I have a database with 3 tables; tblCustomers, tblBookings, tblFlights.
I want to find the customer's last name (LName), from the Customers table where the customers do not appear in the bookings table. It should return just three names, but it returns the names 10 times each. There are 10 records in the bookings table, so I think the command is returning the correct names, but not once...
I have tried:
SELECT tblCustomers.LName
FROM tblCustomers, tblBookings
WHERE tblCustomers.CustID
NOT IN (SELECT CustID FROM tblBookings)
How do I return just one instance of the name, not the name repeated 10 times?
You are doing a CROSS JOIN of the 2 tables.
Use only NOT IN:
SELECT LName
FROM tblCustomers
WHERE CustID NOT IN (SELECT CustID FROM tblBookings)
The (implicit) cross join on The bookings table in the outer query makes no sense - and it multiplies the customer rows.
Also, I would recommend not exists for filtering instead of not in: it usually performs better - with the right index in place, and it is null-safe:
SELECT c.LName
FROM tblCustomers c
WHERE NOT EXISTS (SELECT 1 FROM tblBookings b WHERE b.CustID = c.CustID)
For performance, make sure to have an index on tblBookings(CustID) - if you have a proper foreign key declared, it should already be there.
I'm struggling with this query:
SELECT *
FROM Transactions
WHERE CustomerID IN (SELECT ID FROM Customers
WHERE Name LIKE '%Test%')
It takes 10 seconds to run, however if I create the query manually by taking the 4 values returned by the sub query it runs in milliseconds, for example:
SELECT *
FROM Transactions
WHERE (CustomerID = 1 OR CustomerID = 2 OR
CustomerID = 3 OR CustomerID = 4)
To clarify, running
SELECT ID FROM Customers WHERE Name LIKE '%Test%'
returns the values 1,2,3,4 immediately
Any ideas? What am I missing?
As you already said, when you have the customer id's it runs in milliseconds so the filtering of the customer name is the problem.
The first wildcard (WHERE name LIKE '%Test%') is the suspect here because sql server needs to read all the strings in the name column like a regular expression and find if there is any "Test" in there for every row in the table!
If the names you are filtering for would always start with a "Test" and you could do a WHERE name LIKE 'Test%' it would work much better because sql server only needs to read the start of each string.
Edit:
Here is a little bit different version of the original query if you want to try:
SELECT * FROM Transactions t
WHERE EXISTS (
SELECT 1 FROM
Customers c
WHERE c.ID = t.CustomerID
AND c.Name LIKE '%Test%'
)
What happens with a join?
SELECT t.*
FROM Transactions t JOIN
Customers c
ON t.CustomerID = c.ID
WHERE c.Name Like '%Test%';
Sometimes, JOINs optimize better than IN.
I have 2 database tables:
customers and customers_1
I have 100 customers in the customers table but only 99 customers in the customers_1 table. I would like to write a query that will compare the 2 tables and will result in the missing row.
I have tried this following SQL:
select * from customers c where in (select * from customers_1)
But this will only check for the one table.
Your query shouldn't work this way. You have to compare one column to another and use NOT IN instead of IN:
select *
from customers c
where customerid not in (select customerid from customers_1)
However, Since you are on SQL Server 2008, you can use EXCEPT:
SELECT * FROM customers
EXCEPT
SELECT * FROM customers_1;
This will give you the rows which are in the customers table that are not in customers_1 table:
EXCEPT returns any distinct values from the left query that are not
also found on the right query.
This is easy. Just join them with a left outer join and check for NULL in the table which has the 99 rows. It will look something like this.
SELECT * FROM customers c
LEFT JOIN customers1 c1 ON c.some_key = c1.some_key
WHERE c1.some_key IS NULL
Instead of NOT IN clause consider using NOT EXISTS. NOT EXISTS clause performs better in this particular scenario. Your query would look like:
SELECT * FROM Customer c WHERE NOT EXISTS (SELECT 1 FROM Customer_1 c1 WHERE c.Customer_Id = c1.Customer_Id)
SELECT 1 is just for readability so everyone will know that I don't care about the actual data.
I'm working on an integration project and have created a batchlog table where I store which combinations have been exported already and then check new data against that batchlog table. It worked pretty well as long as I mostly just stored one ID in batchlog table, let's say Customer ID and then selected new rows from Customer table like this:
SELECT *
FROM Customer
WHERE CusId NOT IN (SELECT CusID FROM IntegrationBatchlog)
However, now the solution is more complex and same row from Customer table will be exported several times in combination with other data so now I have couple of separate stored procedures and more columns in IntegrationBatchlog table (CusID, OrdertypeID and PaymentMethod) and join clauses in my select so now it's more like.
SELECT * FROM Customer c
JOIN....
JOIN...
JOIN...
WHERE there is not a row with that CusID AND OrderTypeID AND PaymentMethod in batchlog table yet.
So here I should check whether or not this exact combination has already been exported but how do you do that when you have like three several ID columns in batchlog table and you want to exclude those rows where all the three ID's are already present in same row in batchlog table?
One way is to do a LEFT JOIN to the IntegrationBatchLog table and only insert rows that aren't present.
select *
from Customer c
LEFT OUTER JOIN IntegrationBatchLog i
on c.CusId = i.CusId
and c.OrderTypeID = i.OrderTypeID
and c.PaymentMethod = i.PaymentMethod
where
i.CusId is null
Use EXISTS, not IN. This allows multiple column matching
This is standard SQL
SELECT * FROM Customer c
JOIN....
JOIN...
JOIN...
WHERE NOT EXISTS (
SELECT * FROM IntegrationBatchlog I
WHERE C.CusID = I.CusID
AND C.OrderTypeID = I.OrderTypeID
AND C.PaymentMethod = I.PaymentMethod)
SELECT ...
FROM Customer c JOIN ...
WHERE NOT EXISTS (SELECT *
FROM IntegrationBatchLog I
WHERE I.CusID = c.CusId AND
I.OrderTypeId = c.OrderTypeID ...)
Maybe NOT EXISTS would work here. Here's an example from the MySQL docs (I don't know your DB) - http://dev.mysql.com/doc/refman/5.0/en/exists-and-not-exists-subqueries.html
The second example:
"What kind of store is present in no cities?"
SELECT DISTINCT store_type FROM stores
WHERE NOT EXISTS (SELECT * FROM cities_stores
WHERE cities_stores.store_type = stores.store_type);
Maybe yours could be:
SELECT * FROM Customer c
JOIN....
JOIN...
JOIN...
WHERE NOT EXISTS (
SELECT * FROM batchlog WHERE
c.CusID = batchlog.CusID AND
c.OrderTypeID = batchlog.OrderTypeID AND
c.PaymentMethod = batchlog.PaymentMethod
)