I have a requirement like keep two tables with same name in crate, In mysql we can achieve it using different schema. Any solution like this in crate?
I saw information schema and partitioned table in crate but that not helping me in this case.
actually the current testing release 0.46.0 contains support for schemas! https://groups.google.com/forum/#!topic/crateio/YbYqUQ5iOAc
Related
How could I apply View to enforce backwards compatibility with old queries that rely on old schema if the following change happens:
T(A1(key), A2)
to
T(A1(key), A2(key))
Basically we would make second attribute to be a joined key with first attribute.
Is there any standard way of doing it across diff sql languages?
If not I am interested in SQLite/SQLite3.
Thanks you!
I would have thought that you'd treat this no different to a table, other than not having to worry about the actual data.
That is include it in the older schema to work with the older schema and then upgrade it to the new schema along with the tables by using
DROP VIEW IF EXISTS your_view;
CREATE VIEW IF NOT EXISTS your_view .............;
For other SQL, again as for tables, you may find it simpler to just use the often more extensive ALTER commands.
Without specifics it's hard to say whether or not a single standard method could be adopted.
Context
I have three tables in my SQL Server database: 1) School, 2) College, 3) University.
Then I have another table: Tags.
Each of the three tables (School, College, University) can have Tags associated with them. For which purpose I have three association tables: SchoolTags, CollegeTags, UniversityTags.
Problem
I am trying to create a user-defined function that will take the name of association table as parameter (i.e. 'SchoolTags') and the Id of the entity (school/college/university) and will return a list of tags associated with that entityId.
The issue I am having is I have got to join Tags with a table whose name will come in as parameter. For that I am creating a dynamic query. And we can not run dynamic queries in SQL Server user-defined functions.
Question
Any idea how can that be acheived?
Note: I want separate association tables as I have created and do not want to convert them into a generic association table and I do not want to add If-Else based on table names in my function so that if a new association table is created, I do not need to update my function.
I am using Microsoft SQL Server.
Whatever language you are using, you would probably use if:
begin
if table = 'school' then
begin
. . .
end;
else if table = 'college' then
. . .
end;
The exact syntax depends on the scripting language for the database you are using.
What you desire is impossible. You cannot pass a table name as a parameter to a UDF and use dynamic sql in the UDF to then create and execute a statement that is specific to the table passed as the argument. You already know that you have no choice but to use if-else statements in your UDF to achieve your goal - it is your pipe-dream of "never having to update (or verify) your code when the schema changes" (yes - I rephrased it to make your issue more obvious) that is a problem.
There are likely to be other ways of implementing some useful functionality - but I suggest that you are thinking too far ahead and trying to implement generic functions without a clear purpose. And that is a very difficult and trouble-prone path that requires sophisticated tsql skills.
And to re-iterate the prior responses, you have a schema problem. You purposely created three different entities - and now you want a common function to use with any of them. So before you spend much time on this particular aspect, you should take some time to think carefully about how you intend to use (i.e., write queries against) these tables. If you find yourself using unions frequently to combine these entities into a common resultset, then you have might have a mismatch between your actual business and your model (schema) of it.
Consider normalizing your database in related, logical groupings for one EducationInstitution table and one JoinEducTags table. Those tables sound like they maintain the same structure but of different typology and hence should be saved in one table with different Type field for School, College, University, etc.
Then, add necessary constraints, primary/foreign keys for the one-to-many relationship between all three sets:
You never want to keep restructuring your schema (i.e., add tables) for each new type. With this approach, your user-defined function would just need to receive value parameters not identifiers like tables to be run in dynamic querying. Finally, this approach scales better with efficient storage. And as you will see normalization saves on complex querying.
Need to associate multiple fact tables with a mondrian cube. The schema workbench doesn't allow to do so. How can we achieve this?
You cannot add multiple fact tables in a cube. Schema workbench expects you to have a Star schema in which there will just be one fact table. If you need to combine information from two fact tables on the same subject but with different or same granularity, then you must create a virtual cube. It is easy and very convenient. You can refer to the following documentation:
https://help.pentaho.com/Documentation/6.0/0N0/020/040/000
I'm trying to perform a source to target mapping which essentially maps the original field name to the rename in a view.
Is there a way to do this using information schema? I'm using a postgres database
I do have access to the code, but there are too much interference to use regex to split out what I need.
Thank you for your help
Hi my question is very weird but necessary.
The database was made by a person who named tables and fields like "EMP.EMPCOD0001". Of course that's a low level work but there is no way to change the system and the guy is supported by the company's owner, and IT needs to work properly.
Is it possible to create a kind of shadow table which links to another with reasonable names like: "employee.id_number" pointing to the crappy table?
Use views, e.g.
CREATE VIEW emp.GoodName (goodCol1, goodCol2, goodColEtc)
as SELECT lameCol1, lameCol2, lameColEtc
from emp.LameName
You could put all the views in the dbo schema, but--if it's well thought out or used for security--you might want to maintain the existing schemas.
(Edited to show that columns can be "mapped" as well.)