I have two tables which save data each day.
Table1:
timestamp/id_1/value1/value2
01.01.2020/123/asdf/xyz
02.01.2020/123/asdf/xyz12
03.01.2020/222/asdf/ertw
Table2:
timestamp/id_2/value1/id_1
01.01.2020/345/asdfx/123
02.01.2020/345/asdfy/123
03.01.2020/678/asdfc/222
There is a relationship between both tables:
Table2 * : 1 Table1
The problem when I create the relationship is, that it doesnt recognize the timestamp.
Do you have any idea how to realize setting up the relationship by ID AND by timestamp?
So that:
"02.01.2020/345/asdfy/123" relates to "02.01.2020/123/asdf/xyz12"
and:
"01.01.2020/345/asdfx/123" relates to "01.01.2020/123/asdf/xyz"
Thank you very much!
I am building the data model in PowerBI.
Just concatenate the columns for unique id in power query (or in the source, or sql) and use it for connect
Related
Let me begin by apologizing for what may have been a confusing title. I an just beginning my data analyst journey. I am working in BIGQUERY with a Extreme Storm dataset (TABLE1) that has fields for LAT,LONG, and STATE. There are null values in the latitude and longitude fields that I want to replace with general LAT/LONG values from a State Information dataset(TABLE2) also containing LAT,LONG and STATE values. In TABLE1 each record is given a unique EVENT_ID and there are 1.4m rows. In TABLE2 each STATE is a unique record.
I've tried:
Update TABLE1
SET TABLE1.BEGIN_LAT=TABLE2.latitude
From TABLE1
INNER JOIN TABLE2
ON TABLE1.STATE = TABLE2.STATE
WHERE TABLE1.BEGIN_LAT IS NULL
I am getting an error because TABLE1 contains multiple rows with the same STATE and I am trying to use it as my primary key. I know what I am doing wrong but can't figure out how to do it the correct way. Is what I am trying to do possible in BigQuery?
Any help would be appreciated. Even advice on how to ask questions! :)
Thank you.
I believe you have in your query some alias for TABLE1 in Update and for TABLE1 in From. In this case you can add condition to the WHERE clause to also match on EVENT_ID. Like this:
UPDATE TABLE1 TABLE1_U
SET TABLE1_U.BEGIN_LAT=TABLE2.latitude
FROM TABLE1 TABLE1_F
INNER JOIN TABLE2
ON TABLE1_F.STATE = TABLE2.STATE
WHERE TABLE1_U.BEGIN_LAT IS NULL AND TABLE1_U.EVENT_ID = TABLE1_F.EVENT_ID
Also, I would prefer to do SELECT query instead of update and save query results to the new table.
I have 2 tables, one is for the categories and the other is for the particulars of the corresponding categories.
I need all categories to be shown with their corresponding particulars.
I am not clear about your question and i assume you are using sql server
select t1.category,t2.particularname from categories t1 left join particulars t2 on t1.categoryid=t2.categoryid
From what you said, it seems Categories table has one-to-many relation with particulars. That means Primary Key of Categories should be refered in particulars as Foreign Key in Particulars. You can use following Query to join
SELECT * FROM categories C JOIN particulars P ON C.cat_id = P.cat_id;
And you should rename if some other columns in both tables have same name and you don't want them to be a part of JOIN.
For more example on JOIN.
Originally, I have 2 tables. I normalized it since the relationship of this tables is many to many. Now I have 3.
Jobs
jID PK
jName
jDesc
jEarnings
jTags
Course
cID PK
cName
cDesc
cSchool
cProgram
JobsCourse
ID PK
jID FK
cID FK
My app displays a tableview of the jobs
When clicked it displays the UIViewcontroller of jobs plus a tableview of the related course
How do I query the jobcourse table so that I can get all the related Courses to a certain job?
You can join the two tables, e.g.:
SELECT course.* FROM course INNER JOIN jobscourse ON jobscourse.cID = course.cID WHERE jobscourse.jID = ?
That gets all entries from course where the jID in jobscourse is equal to some value.
In my ETL process I am using Change Data Capture (CDC) to discover only rows that have been changed in the source tables since the last extraction. Then I do the transformation only for this rows. The problem is when I have for example 2 tables which I want to join into one dimension, and only one of them has changed. For example I have table Countries and Towns as following:
Countries:
ID Name
1 France
Towns:
ID Name Country_ID
1 Lyon 1
Now lets say a new row is added to Towns table:
ID Name Country_ID
1 Lyon 1
2 Paris 2
The Countries table has not been changed, so CDC for these tables shows me only the row from Towns table. The problem is when I do the join between Countries and Towns, there is no row in Countries change set, so the join will result in empty set.
Do you have an idea how to solve it? Of course there might be more difficult cases, involving 3 and more tables, and consequential joins.
This is a typical problem found when doing Realtime Change-Data-Capture, or even Incremental-only daily changes.
There's multiple ways to solve this.
One way would be to do your joins on the natural keys in the dimension or mapping table, to get the associated country (SELECT distinct country_name, [..other attributes..] from dim_table where country_id = X).
Another alternative would be to do the join as part of the change capture process - when a row is loaded to towns, a trigger goes off that loads the foreign key values into the associated staging tables (country, etc).
There is allot i could babble on for more information on but i will be specific to what is in your question. I would suggest the following to get the results...
1st Pass is where everything matches via the join...
Union All
2nd Pass Gets all towns where there isn't a country
(left outer join with a where condition that
requires the ID in the countries table to be null/missing).
You would default the Country ID value in that unmatched join to something designated as a "Unmatched Value" typically 0 or -1 is used or a series of standard -negative numbers that you could assign descriptions to later to identify why data is bad for your example -1 could be "Found Town Without Country".
If I have many to many relation ship in database witch is looking like that:
House-HouseType-Type
In data model it is looking like that
House-Type
I cant modify table HouseType directly because there is no entity for that.
For example if I have insert some entities in database after records in table HouseType looking like that:
HouseId TypeId
1 2
1 3
1 4
than I want to remove some relations records.
e.g Records in table after remove would be:
HouseId TypeId
1 2
How can I do that in Entity Framework 4 ?
house.Types.Remove(type)
or
type.Houses.Remove(house)