I need to write a query, and I'm not sure where to start... A join won't work since I'm basically querying for everything from both tables (for one column).
I have 2 tables, Each table different fields. But each table has 1 field in common i.e. Domains, I need to pull a list of all domains between both of them and return it in 1 column.
So table 1's domain field, and table 2's domain field showing in 1 column below eachother.
Also removing duplicates where there are. So if there's 2 domains that both are the same, I only need to show 1.
Is something like this possible in a SQL Query?
Related
I have the following problem.
I have a table Entries that contains 2 columns:
EntryID - unique identifier
Name - some name
I have another EntriesMapping table (many to many mapping table) that contains 2 columns :
EntryID that refers to the EntryID of the Entries table
PartID that refers to a PartID in a seprate Parts table.
I need to write a SP that will return all data from Entries table, but for each row in the Entries table I want to provide a list of all PartID's that are registered in the EntriesMapping table.
My question is how do I best approach the deisgn of the solution to this, given that the results of the SP would regularly be processed by an app so performance is quite important.
1.
Do I write a SP that will select multiple rows per entry - where if there are more than one PartID's registered for a given entry - I will return multiple rows each having the same EntryID and Name but different PartID's
OR
2.
Do I write a SP that will select 1 row per entry in the Entries table, and have a field that is a string/xml/json that contains all the different PartID's.
OR
3. There is some other solution that I am not thinking of?
Solution 1 seems to me to be the better way to go, but I will be passing lots of repeating data.
Solution 2 wont pass extra data, but the string/json/xml would need to be processed additionally, resuling in larger cpu time per item.
PS: I feel like this is quite a common problem to solve, but I was unable to find any resource that can provide common solutions or some pros/cons to different approaches.
I think you need simple JOIN:
SELECT e.EntryId, e.Name, em.PartId
FROM Entries e
JOIN EntriesMapping em ON e.EntryId = em.EntryId
This will return what you want, no need for stored procedure for that.
I'm trying to achieve 2 joins. If I run the 1st join alone it pulls 4 lots of results, which is correct. However when I add the 2nd join which queries the same reference table using the results from the select statement it pulls in additional results. Please see attached. The squared section should not be being returned
So I removed the 2nd join to try and explain better. See pic2. I'm trying to get another column which looks up InvolvedInternalID against the initial reference table IRIS.Practice.idvClient.
Your database is simply doing as you tell it. When you add in the second join (confusingly aliased as tb1 in a 3 table query) the database is finding matching rows that obey the predicate/truth statement in the ON part of the join
If you don't want those rows in there then one of two things must be the case:
1) The truth you specified in the ON clause is faulty; for example saying SELECT * FROM person INNER JOIN shoes ON person.age = shoes.size is faulty - two people with age 13 and two shoes with size 13 will produce 4 results, and shoe size has nothing to do with age anyway
2) There were rows in the table joined in that didn't apply to the results you were looking for, but you forgot to filter them out by putting some WHERE (or additional restriction in the ON) clause. Example, a table holds all historical data as well as current, and the current record is the one with a NULL in the DeletedOn column. If you forget to say WHERE deletedon IS NULL then your data will multiply as all the past rows that don't apply to your query are brought in
Don't alias tables with tbX, tbY etc.. Make the names meaningful! Not only do aliases like tbX have no relation to the original table name (so you encounter tbX, and then have to go searching the rest of the query to find where it's declared so you can say "ah, it's the addresses table") but in this case you join idvclient in twice, but give them unhelpful aliases like tb1, tb3 when really you should have aliased them with something that describes the relationship between them and the rest of the query tables
For example, ParentClient and SubClient or OriginatingClient/HandlingClient would be better names, if these tables are in some relationship with each other.
Whatever the purpose of joining this table in twice is, alias it in relation to the purpose. It may make what you've done wriong easier to spot, for example "oh, of course.. i'm missing a WHERE parentclient.type = 'parent'" (or WHERE handlingclient.handlingdate is not null etc..)
The first step to wisdom is by calling things their proper names
Trying to create relationships (joins) between tables in power pivot.
Got 2 tables I wold like to join together, connected with a common column = CustomerID.
One is a Fact Table the other Dim table (look up).
I have run the "remove duplicates" on both tables without any problem.
But I still get an error saying : "the relationship cannot be created because each column contains duplicate values. Select at least one column that contains only unique values".
The Fact Table contains duplicates (as it should?) and the Dim Table do not, why do I get this error?
Help much appreciated
Created an appended table with both columns "CustomerID". After the columns where appended together I could "remove duplicates" and connect the tables together through the newly created appended table.
Don't know if this causes another problem later however.
You can also check for duplicate id values in a column by using the group by feature.
Remove all columns except ID, add a column that consists only of the number 1.
Group by ID, summing the content of the added column and filter out IDs whose total equals 1. What's left are duplicated IDs.
I have 3 tables that work, let's say, as levels for this purpose. Everyone of them has 2 columns, id and name. And, they combined, result on posibilities that matches the table 4.
How can I create the relationships between the first set (3 tables), and the last one with the possible results after the combination?
I did this in the past just with 2 tables, back then I created a third one having 2 fields, 2 FKs against the original tables. But this time, I have a set of 3 tables to match with a fourth, and that's what's making me wonder.
Should I simply create a 5th table with 4 fields having 4 FKs or is there another way?
Use a 5th table as an assignment table, then using a nested query with joins you can access the data in your results table
note, the 5th table would have 3 FK columns linked to the 3 other tables, and a 4th for a row id.
We have a huge table and one of the column contains queries like e.g. in row 1
1. (((firstname:Adam OR firstname:Neil ) AND lastname:Lee) ) AND category:"Legal" AND type:Individual
and in row 2 of same column
2. (((firstname:Adam* OR firstname:Neil ) AND lastname:Lee) ) AND category:"Legal" AND type:Organization
Similarly there are few other types of Query strings which are used eventually to query external services.
Issue is based on certain criteria I have to group and remove duplicates from this table.
There are few rules to determine grouping of Strings in different rows.One of them is that if first name and lastname are same then ignore category and type values, therefore above two rows will be grouped to one. There are around million rows. Comparing Strings and doing grouping is not looking elegant solution. What could be best possible solution using sql.