I have two tables.
Order
Replication.
A single order record can have multiple Replication records. I want to join these two tables, such that i always retrieve a single record out of the join even if multiple records exist.
Sample data
Replication table:
ORDID | STATUS | ID | ERRORMSG | HTTPSTATUS | DELIVERYCNT
=========================================================
1717410307 1 JBM-9e92ae0c NULL 200 1
----------
1717410307 1 JBM-9fb59af1 NULL 400 -99
----------
1717410308 1 JBM-0764b091 NULL 403 1
----------
1717410308 1 JBM-0764b091 NULL 200 1
Order Table:
ORDID | ORDTYPE | DATE
----------
1717410307 CAR 22-SEP-2011
1717410308 BUS 23-SEP-2011
How can i make a join effectively so as , i will get as many records in order table and a replication table that should be dynamically selected on a priority basis.
The priority can be defined as :
Any record with a delivery count of -99
HTTPSTATUS != 200
Please guide me how can i proceed with this joining?
Please let me know if you need any clarification.
Your help is much appreciated!
Is it possible to use ORDER BY clause based on the HTTPSTATUS and DELIVERYCNT?
In that case you can write a specific ORDER BY and getting the TOP 1 from it (don't know which RDBMS do you use) or getting ROW_NUMBER() OVER (ORDER BY ... ) AS RowN WHERE RowN = 1
But this is the ugly (yet quick) solution.
The other option is to make a subquery where you add a new column which will make the priority calculation.
To make the query effective you should consider indexing (or using RDBMS specific solutions like included columns)
Related
How to vertically flip the column values from top to bottom in SQL which are not in any specific order(neither asc nor desc)?
Example: Table named 'Country' has a single column c1 with values
| C1 |
---------
| JAPAN |
| NEPAL |
| INDIA |
---------
Now I want to display the Result-set as below:
| C1 |
----------
| INDIA |
| NEPAL |
| JAPAN |
----------
If anyone can kindly suggest?
It's not possible using standard SQL (at least before 2003) because when not explicitly ordered using ORDER BY, a resultset is an "unordered set".
This means that the order you'll get your results is supposed to be totally random and may vary from a call to a given query to the next call to this same query. Most of the time, though, you'll simply get them the way they have been inserted into the database, but this is not guaranteed. When using advanced RDBMs, you may for instance get your entries sorted according to the last ORDER BY you did before.
That's also why you don't get any row number when querying a table. Because it just doesn't make sense.
However, since SQL 2003, OLAP functions have been introduced, including ROW_NUMBER(). For the reasons exposed above, it has to be "windowed" using an OVER clause, which breaks initial order. But you still can lean on a subquery to fetch them all, joining aside a column that will never vary:
WITH subquery(c1,c2) AS (SELECT C1,1 AS C2 FROM yourtable)
SELECT c1
FROM subquery
ORDER BY row_number() OVER (PARTITION BY c2) DESC
Don't use RANK() as this will return the same "ex-æquo" row number if two rows are identical.
I have tables in which are banking operations and other tables with the amount of operations.
Operation Id | name operation
-------------+----------------
0 | transfer
1 | registration
2 | BLIK
Operation Id | amount
-------------+--------
0 | 15,000
1 | 53,000
2 | 200
E.t.c
I was supposed to write a query that shows the names of the operations in the form of a column together with the amount. Well, I wrote something like this:
Select
case id_operacji
when 0 then amount
end as 'transfer',
case id_operacji
when 1 then amount
end as 'registration ',
case operation id
when 2 then amount of operation
end as 'BLIK'
from ...
In response to the above solution I received information that the main problem is to check that the header will depend on the change of the operation name. Could someone help me how to do it?
As far as I can tell, you are looking for JOIN between the two tables:
select a.amount, o.name_operation
from operations o
join amounts a on o.operation_id = a.operation_id;
I had to guess the table and column names as you did not disclose the real table structures.
I take a Database course in which we have listings of AirBnBs and need to be able to do some SQL queries in the Relationship-Model we made from the data, but I struggle with one in particular :
I have two tables that we are interested in, Billing and Amenities. The first one have the id and price of listings, the second have id and wifi (let's say, to simplify, that it equals 1 if there is Wifi, 0 otherwise). Both have other attributes that we don't really care about here.
So the query is, "What is the difference in the average price of listings with and without Wifi ?"
My idea was to build to JOIN-tables, one with listings that have wifi, the other without, and compare them easily :
SELECT avg(B.price - A.price) as averagePrice
FROM (
SELECT Billing.price, Billing.id
FROM Billing
INNER JOIN Amenities
ON Billing.id = Amenities.id
WHERE Amenities.wifi = 0
) A, (
SELECT Billing.price, Billing.id
FROM Billing
INNER JOIN Amenities
ON Billing.id = Amenities.id
WHERE Amenities.wifi = 1) B
WHERE A.id = B.id;
Obviously this doesn't work... I am pretty sure that there is a far easier solution to it tho, what do I miss ?
(And by the way, is there a way to compute the absolute between the difference of price ?)
I hope that I was clear enough, thank you for your time !
Edit : As mentionned in the comments, forgot to say that, but both tables have idas their primary key, so that there is one row per listing.
Just use conditional aggregation:
SELECT AVG(CASE WHEN a.wifi = 0 THEN b.price END) as avg_no_wifi,
AVG(CASE WHEN a.wifi = 1 THEN b.price END) as avg_wifi
FROM Billing b JOIN
Amenities a
ON b.id = a.id
WHERE a.wifi IN (0, 1);
You can use a - if you want the difference instead of the specific values.
Let's assume we're working with data like the following (problems with your data model are noted below):
Billing
+------------+---------+
| listing_id | price |
+------------+---------+
| 1 | 1500.00 |
| 2 | 1700.00 |
| 3 | 1800.00 |
| 4 | 1900.00 |
+------------+---------+
Amenities
+------------+------+
| listing_id | wifi |
+------------+------+
| 1 | 1 |
| 2 | 1 |
| 3 | 0 |
+------------+------+
Notice that I changed "id" to "listing_id" to make it clear what it was (using "id" as an attribute name is problematic anyways). Also, note that one listing doesn't have an entry in the Amenities table. Depending on your data, that may or may not be a concern (again, refer to the bottom for a discussion of your data model).
Based on this data, your averages should be as follows:
Listings with wifi average $1600 (Listings 1 and 2)
Listings without wifi (just 3) average 1800).
So the difference would be $200.
To achieve this result in SQL, it may be helpful to first get the average cost per amenity (whether wifi is offered). This would be obtained with the following query:
SELECT
Amenities.wifi AS has_wifi,
AVG(Billing.price) AS avg_cost
FROM Billing
INNER JOIN Amenities ON
Amenities.listing_id = Billing.listing_id
GROUP BY Amenities.wifi
which gives you the following results:
+----------+-----------------------+
| has_wifi | avg_cost |
+----------+-----------------------+
| 0 | 1800.0000000000000000 |
| 1 | 1600.0000000000000000 |
+----------+-----------------------+
So far so good. So now we need to calculate the difference between these 2 rows. There are a number of different ways to do this, but one is to use a CASE expression to make one of the values negative, and then simply take the SUM of the result (note that I'm using a CTE, but you can also use a sub-query):
WITH
avg_by_wifi(has_wifi, avg_cost) AS
(
SELECT Amenities.wifi, AVG(Billing.price)
FROM Billing
INNER JOIN Amenities ON
Amenities.listing_id = Billing.listing_id
GROUP BY Amenities.wifi
)
SELECT
ABS(SUM
(
CASE
WHEN has_wifi = 1 THEN avg_cost
ELSE -1 * avg_cost
END
))
FROM avg_by_wifi
which gives us the expected value of 200.
Now regarding your data model:
If both your Billing and Amenities table only have 1 row for each listing, it makes sense to combine them into 1 table. For example: Listings(listing_id, price, wifi)
However, this is still problematic, because you probably have a bunch of other amenities you want to model (pool, sauna, etc.) So you might want to model a many-to-many relationship between listings and amenities using an intermediate table:
Listings(listing_id, price)
Amenities(amenity_id, amenity_name)
ListingsAmenities(listing_id, amenity_id)
This way, you could list multiple amenities for a given listing without having to add additional columns. It also becomes easy to store additional information about an amenity: What's the wifi password? How deep is the pool? etc.
Of course, using this model makes your original query (difference in average cost of listings by wifi) a bit tricker, but definitely still doable.
I wonder which has better performance in this case. First of all, I want to show to the user his medical information. I have two tables
user
-----
id_user | type_blood | number | ...
1 O 123
2 A+ 442
user_allergies
-----------
id_user | name
1 name1
1 name2
I want to return:
JSON {id_user=1, type_blood=0, allergies=(name1,name2)}
So, Its better do a JOIN for user and user_allergies and iterate, or maybe two SELECT?
But if then I have another table like user_allergies, that the result can be:
user_another_table
-----------
id_user | name
1 namet1
1 namet2
1 namet3
JSON {id_user=1, type_blood=0, allergies=(name1,name2), table=(namet1,namet2,namet3)}
It's better three SELECT or a JOIN, but then I have to iterate on the results and I can't imagine a esay way. A JOIN can give me a result like:
id_user | type_blood | allergy_name | another_table_name
1 O name1 namet1
1 O name1 namet2
1 O name1 namet3
1 O name2 namet1
1 O name2 namet2
1 O name2 namet3
Is there any way to extract:
id_user | type_blood | allergy_name | another_table_name
1 O name1 namet1
1 O name2 namet2
1 O namet3
Thanks community, I'm newbie in SQL
Depending on the data - there is no way to get the 2nd set of results you've shown, if the 1st set of results shows the values. The 2nd one is throwing data away - in this case allergy 'name2' for another_table_name 'namet3'. This is why you get many rows back with repeated data.
You can use the group by clause to restrict this in some cases, but again - it won't let you throw away data like that.
You could try using the COALESCE clause, if your DB supports it.
If not, I think you're going to have to construct your JSON in some business logic, in which case its fine to read the data in a 3-way join. You order by the user id and either create or append the row data to the JSON document depending if a user record is present or not (if you order by user id, you only need to keep track of when the user id value changes).
Alternatively, you can read a list of users and single-item data in one query, and then ht the DB again for the repeating data.
I have two tables in an Access database, tblProducts and tblProductGroups.
I am trying to run a query that joins both of these tables, and brings back a single record for each product. The problem is that the current design allows for a product to be listed in the tblProductGroups table more than 1 - i.e. a product can be a member of more than one group (i didnt design this!)
The query is this:
select tblProducts.intID, tblProducts.strTitle, tblProductGroups.intGroup
from tblProducts
inner join tblProductGroups on tblProducts.intID = tblProductGroups.intProduct
where tblProductGroups.intGroup = 56
and tblProducts.blnActive
order by tblProducts.intSort asc, tblProducts.curPrice asc
At the moment this returns results such as:
intID | strTitle | intGroup
1 | Product 1 | 1
1 | Product 1 | 2
2 | Product 2 | 1
2 | Product 2 | 2
Whereas I only want the join to be based on the first matching record, so that would return:
intID | strTitle | intGroup
1 | Product 1 | 1
2 | Product 2 | 1
Is this possible in Access?
Thanks in advance
Al
This option runs a subquery to find the minimum intGoup for each tblProducts.intID.
SELECT tblProducts.intID
, tblProducts.strTitle
, (SELECT TOP 1 intGroup
FROM tblProductGroups
WHERE intProduct=tblProducts.intID
ORDER BY intGroup ASC) AS intGroup
FROM tblProducts
WHERE tblProducts.blnActive
ORDER BY tblProducts.intSort ASC, tblProducts.curPrice ASC
This works for me. Maybe this helps someone:
SELECT
a.Lagerort_ID,
FIRST(a.Regal) AS frstRegal,
FIRST(a.Fachboden) AS frstFachboden,
FIRST(a.xOffset) AS frstxOffset,
FIRST(a.yOffset) AS frstyOffset,
FIRST(a.xSize) AS frstxSize,
FIRST(a.ySize) AS frstySize,
FIRST(a.Platzgr) AS frstyPlatzgr,
FIRST(b.Artikel_ID) AS frstArtikel_ID,
FIRST(b.Menge) AS frstMenge,
FIRST(c.Breite) AS frstBreite,
FIRST(c.Tiefe) AS frstTiefe,
FIRST(a.Fachboden_ID) AS frstFachboden_ID,
FIRST(b.BewegungsDatum) AS frstBewegungsDatum,
FIRST(b.ErzeugungsDatum) AS frstErzeugungsDatum
FROM ((Lagerort AS a)
LEFT JOIN LO_zu_ART AS b ON a.Lagerort_ID = b.Lagerort_ID)
LEFT JOIN Regal AS c ON a.Regal = c.Regal
GROUP BY a.Lagerort_ID
ORDER BY FIRST(a.Regal), FIRST(a.Fachboden), FIRST(a.xOffset), FIRST(a.yOffset);
I have non unique entries for Lagerort_ID on the table LO_zu_ART. My goal was to only use the first found entry from LO_zu_ART to match into Lagerort.
The trick is to use FIRST() an any column but the grouped one. This may also work with MIN() or MAX(), but I have not tested it.
Also make sure to call the Fields with the "AS" statement different than the original field. I used frstFIELDNAME. This is important, otherwise I got errors.
Create a new query, qryFirstGroupPerProduct:
SELECT intProduct, Min(intGroup) AS lowest_group
FROM tblProductGroups
GROUP BY intProduct;
Then JOIN qryFirstGroupPerProduct (instead of tblProductsGroups) to tblProducts.
Or you could do it as a subquery instead of a separate saved query, if you prefer.
It's not very optimal, but if you're bringing in a few thousand records this will work:
Create a query that gets the max of tblProducts.intID from one table and call it qry_Temp.
Create another query and join qry_temp to the table you are trying to join against, and you should get your results.