I have two tables that I try to join over one field and it gives me different results in two queries that should give same results. Queries are:
SELECT * FROM tblCustomer tca
WHERE tca.PhoneNumber IN(
SELECT ts.SubscriptionNumber FROM sub.tblSubscription ts
WHERE ts.ServiceTypeID=4
AND ts.SourceID=-1
)
and
SELECT tca.*
FROM sub.tblSubscription ts
inner JOIN tblCustomer tca
ON ts.SubscriptionNumber = tca.PhoneNumber
WHERE ts.ServiceTypeID = 4
AND ts.SourceID = -1
How is this possible?
I'm assuming a customer can have multiple subscriptions, right? Let's assume you have 5 customers, each with 2 subscriptions...
When doing a SELECT ... FROM Customer WHERE IN (Subscription), you will receive 5 customer records, because each of those 5 customers are in fact in the subscription table, even though the subscription table will have 10 records. You are inherently asking the database for the data from one table, where the value of one of it's fields exists in another table. So it will only return the distinct records in the FROM table, irrespective of the amount of data in the WHERE IN table.
On the other hand, INNER JOINing the Customer table with the subscription table will return 5 customers x 2 subscriptions each = 10 records. By JOINing the tables you are asking the database for ALL the data in each table, where the data is matched up against specific fields.
So yes, the 2 queries will definitely give you different results.
Related
Hi guys I'm new with databases and I'm trying to make a query where I join 3 tables. I could make it and I want to clean up the result. I want to know how can I delete the column "pin" from users table and maybe some "ids" columns.
Select * from "wish-list"
Join products
On "wish-list".id = products.holiday_id
Join users
On "wish-list".user_id = users.id
Where "wish-list".id = 1
You need to specify which columns you really need in your output. At the moment you are using
SELECT * which outputs all columns of all joined tables.
Here is what it should look like:
SELECT holiday, products.description, users.pin FROM "wish-list"
JOIN products ON "wish-list".id = products.holiday_id
JOIN users ON "wish-list".user_id = users.id
WHERE "wish-list".id = 1
It's important that you reference all columns which are not your main entity (here wish-list) with tablename.column (products.description and not only description). It will work without referencing strictly but only if the column name is unique in your query.
Furthermore you can rename columns. This is useful for example if you want to get the id's of the product table and the wish-list table.
SELECT product.id AS product_id, id AS wishlist_id FROM "wish-list"
...
Hope that helps!
I have 2 tables that I am attempting to join but to only display rows of data based on specific parameters.
Table one: "orders"
Table two: "cash_tracking"
Matching parameters from both tables: "orders.user_id" and "cash_tracking.user_id" and the user_id is 2640
The result I want to see is all the "orders.name" from the "user_id=2640" on a specific shop "shop_id = 7777" and based on a specific register number from the "cash_tracking" table eg. "cash_transaction_reg=444454"
However, when I run my query it shows me every single order on this shop instead of the ones related to the user 2640 on this specific register - 444454
Here is what I have so far:
SELECT orders.name
FROM orders
Inner JOIN cash_tracking
ON orders.user_id = cash_tracking.user_id
WHERE orders.shop_id = 7777
AND cash_tracking.user_id=2640
AND cash_tracking.cash_transaction_reg=444454
You select all orders for user_id, shoud be some join orders.Id = cash_tracking.OrderId
I have a select query which combined several tables. PRODUCTION_ORDER_RESULTS, PRODUCTION_ORDERS and SERVICE_GUARANTY_NEW have common value however STOCKS table does not.
SELECT PR_ORDERS.ARRIVED_CITY,
PR_ORDERS.MONTAJ_DATE,
PR_ORDER_RESULT.TRANSFER_DATE,
PR_ORDERS.P_ORDER_ID,
PR_ORDER_RESULT.P_ORDER_ID,
SG.SALE_CONSUMER_ID,
SG.IS_SERI_SONU,
S.BRAND_ID,
S.PROPERTY
FROM workcube_test_1.PRODUCTION_ORDER_RESULTS PR_ORDER_RESULT,
workcube_test_1.PRODUCTION_ORDERS PR_ORDERS,
workcube_test_1.SERVICE_GUARANTY_NEW SG,
workcube_test_1.STOCKS S
WHERE PR_ORDER_RESULT.P_ORDER_ID = PR_ORDERS.P_ORDER_ID
AND PR_ORDER_RESULT.PR_ORDER_ID = SG.PROCESS_ID
when I run the query, it shows the output as below.
The problem here is there are four data rows returned from PRODUCTION_ORDER_RESULTS, PRODUCTION_ORDERS, SERVICE_GUARANTY_NEW and once I have added the STOCKS table, arrived_city, montaj_date, transfer_date columns are side by side with STOCKS table's rows, but the columns value should be null, not filled with data.
The way I tried is UNION of STOCKS table, however unioned table values are ignored, can not use them in html blocks.
there needs to be at least one more join condition among tables where there's for STOCKS table, I think there might exist such a column STOCK_ID within a table such as PRODUCTION_ORDER_RESULTS in order to join with STOCKS table. I think this should be the reason for multiple returning rows. If there's no common column, then the returning data will be produced as many as the number of records within STOCK table due to existing CROSS JOIN logic within the current query. So rearrange your query as
SELECT PR_ORDERS.ARRIVED_CITY,
PR_ORDERS.MONTAJ_DATE,
PR_ORDER_RESULT.TRANSFER_DATE,
PR_ORDERS.P_ORDER_ID,
PR_ORDER_RESULT.P_ORDER_ID,
SG.SALE_CONSUMER_ID,
SG.IS_SERI_SONU,
S.BRAND_ID,
S.PROPERTY
FROM workcube_test_1.PRODUCTION_ORDER_RESULTS PR_ORDER_RESULT
JOIN workcube_test_1.PRODUCTION_ORDERS PR_ORDERS
ON PR_ORDER_RESULT.P_ORDER_ID = PR_ORDERS.P_ORDER_ID
JOIN workcube_test_1.SERVICE_GUARANTY_NEW SG
ON PR_ORDER_RESULT.PR_ORDER_ID = SG.PROCESS_ID
JOIN workcube_test_1.STOCKS S
ON PR_ORDER_RESULT.STOCK_ID = S.ID
I need to join two tables on two different fields. I have table 1 like this:
key productid customer
1 100 jhon
2 109 paul
3 100 john
And table 2 has same fields but aditional data I must relate to first table
key productid customer status date ...
1 109 phil ok 04/01
2 109 paul nok 04/03
3 100 jhon nok 04/06
4 100 jhon ok 04/06
Both "key" fields are autoincrement. Problem is that my relationship fields are repeated several times across result and I need to generate a one-to-one relationship, in such manner that one row from table 2 must be related ONLY ONCE with a row on table 1.
I did a left join on (customer=customer and productid=productid) but relationship came out duplicated, a row from tablet 2 was related many times to rows of table one.
To clarify things...
I have to cross check both tables, table 1 is loaded from an XLS report, table 2 is data from a database that reflects customer transactions with many status data. I have to check if a row from XLS exists in database and then load additional status data. I must produce a report when rows from XLS has no correspondent data on database.
How can accomplish this JOIN, is this possible with only SQL?
You can accomplish this in MS SQL using the sql below. Not sure if SQLite supports this.
select a.*, c.*
from table2 a, ( select min(key) key, productid, customer
from table1
group by productid, customer
) b,
table1 c
where a.productid = b.productid
and a.customer = b.customer
and b.key = c.key
One way to understand this would be to figure out what each table represents exactly. Both tables seem to represent the same thing, with a row representing what you might call a purchase. Why are there two separate tables, then? Perhaps the second table goes into more depth about each purchase? Like jhon bought product 100, and it was 'nok' first and then 'ok'? Is so, then the key (what makes the table unique) for the second table would be all three fields.
You still join on only the two fields that match, but you can't expect uniqueness if there are two rows with the same unique keys.
It helps sometimes to create additional indexes on a table, to see what is truly unique.
Hi am I am creating a database which allows users to make a reservation to a restaurant. Below is my data model for the database.
My question is i am a little confused with how i would check for tables that are available on a given night. The restaurant has 15 tables for any night with 4 people to a table (Groups can be 4 - 6 big, groups larger than 4 will take up two tables).
How would i query the database to return the tables which are available on a given night.
Thanks.
EDIT::
This is what i have tried. (Some of it is pseudo as i am not quite sure how to do it)
SELECT tables.table_id
FROM tables
LEFT JOIN table_allocation
ON tables.table_id = table_allocation.table_id
WHERE table_allocation.table_id is NULL;
This returns the well empty rows as it is checking for the none presence of the table. I am not quite sure how i would do the date bit test.
To find TABLE rows that have no TABLE_ALLOCATION rows on a given THEMED_NIGHT.TEME_NIGHT_DATE, you should be able to do something like this:
SELECT *
FROM TABLES
WHERE
TABLE_ID NOT IN (
SELECT TABLE_ALLOCATION.TABLE_ID
FROM
TABLE_ALLOCATION
JOIN RESERVATION
ON TABLE_ALLOCATION.RESERVATION_ID = RESERVATION.RESERVATION_ID
JOIN THEMED_NIGHT
ON RESERVATION.THEME_ID = THEMED_NIGHT.THEME_ID
WHERE
THEME_NIGHT_NAME = :the_date
)
In plain English:
Join TABLE_ALLOCATION, RESERVATION and THEMED_NIGHT and accept only those that are on the given date (:the_date).
Discard the TABLE rows that are related to the tuples above (NOT IN).
Those TABLE rows that remain are free for the night.
Try:
SELECT tables.table_id
FROM tables t
WHERE NOT EXISTS
(SELECT NULL
FROM table_allocation a
JOIN reservation r
ON a.reservation_id = r.reservation_id and
r.`TIME` between :Date and :Date+1
WHERE t.table_id = a.table_id)
Note: will only return tables that are not booked at any point on the day in question.