I´m quite new to the Oracle SQL Developer. I try to handle a big database and I need to define views. Therefore, I need the relationships of some tables. with the relational models of the Browser, I´m able to show ALL relationships of the table, which is quite confusing.
Is there a way to show the ralationships of just one column?
I want to pick the table and the column and I want to see to which other tables the column is connected.
Thank you.
My suggestion:
First find out in which tables the column name has been used :
select * from all_tab_columns where column_name='COLUMN_NAME';
And then you can see constraints defined for the respective columns in that tables
Related
I'm interested in getting the structure of each table in my DB.
Currently I'm using: DESCRIBE TABLE table1.
However, this means I have to do a separate query for each table. Was wondering whether there is a query I can get the structure of several tables at once (and therefore saving me some queries)?
Thanks,
Nir.
You can use Account Usage/Information Schema view COLUMNS
https://docs.snowflake.com/en/sql-reference/account-usage/columns.html
Following article have a slight difference example of using COLUMNS view to create a select statement but it should give you an idea
https://community.snowflake.com/s/article/Select-columns-based-on-condition-in-Snowflake-using-Information-Schema-and-Stored-Procedure
You have a couple options:
you can use the COLUMNS view in the information schema
https://docs.snowflake.com/en/sql-reference/info-schema/columns.html
Note: The view only displays objects for which the current role for the session has been granted access privileges.
you can use the COLUMNS view in the account_usage share schema:
https://docs.snowflake.com/en/sql-reference/account-usage/columns.html
Note: this will show all the columns in all tables, will show deleted objects and such as well.
Also note, there is a delay in the data (latency could be as much as 90 minutes, typically isn't though)
I have two Azure SQL Server databases with the following as example:
Database Name: DataProp
Table Name: DataImports
Columns: SearchID, SourceID, Text, Status, Country
Database Name: Sources
Table Name: SourceInformation
Columns: SourceID, SourceTitle, Country
Right now, the Country column in the DataProp database is all NULL. I need to auto-populate the Country field in DataProp with the values of the Country fields in the Sources database. The common field between the two tables is SourceID. I need to do this for all existing data, as well as have it occur for future records.
What is the best way to accomplish this? A stored procedure that's set to run on a schedule? If so, I would appreciate guidance on the T-SQL syntax.
As a side-note, I looked at the possibility of a computed column, but this will not work for us b/c we maintain an Azure Search Index on our tables, and Azure Search can't index computed columns.
I don't think you'll be able to directly write a join between tables in two different DBs. We had a similar problem and decided to move all tables into a single DB in separate schemas. I think in your case you can write a Webjob to pull in data from one table and update the second table. I also found one article related to this but haven't personally tried, so not sure if it works.
https://ppolyzos.com/2016/07/30/cross-database-queries-in-azure-sql-databases/
I am working on a project, where a user will select a a table choice on a website. Once the table is selected, the website will then connect to the database and select the table from a server (Server A) under a database (ABC). The website will also have to choose the same table from a different server (Server B) under database (DEF). Also these tables will have the same name, they will have some different data entered into them.
Our goal is to come up with a dynamic SQL Query/Stored Procedure. Multiple table choices can be visible in the website and once the user picks an option, it DYNAMICALLY passes that information to the database to find the two tables and yield a final table that portrays the differences.
MY PROBLEM:
I am having a lot of problem with the syntax and doing this process dynamically. I have searched everywhere for a solution and am struggling with this for more than two weeks.
OUTLINE OF MY PLAN:
Find primary keys and the column names of all the columns in a selected table. Pass this information to a temporary table
Create a SQL query with something like :
SET #SQL = select table1.col1, table2.col1... inner join..
Take care of conditions where :
A. Data is present in one table but not the other
B. Data is present in both tables
C. What if there is no data in one or both tables.
I would really appreciate any help. I am very new to SQL and have been trying my hardest in this project for a while. Please help me and I will do my best to repay you. Thank you very much for your time.
I know in SQL Server you can create indexes on a view, then the view saves the data from the underlying table. Then you can query the view. But, why I need to use view instead of table?
You may want to use a view to simplify on queries. In our projects, the consensus is on using views for interfaces, and especially "report interfaces".
Imagine you've got a client table, and the manager wants a report every morning with the client's name, and their account balance (or whatever). If you code your report against the table, you're creating a strong link between your report and your table, making later changes difficult.
On the other hand if your report hits a view, you can twist the database freely; as long as the view is the same the report works, the manager is happy and you're free to experiment with the database. You want to separate client metadata from the main client table? go for it, and join the two tables in the view. You want to denormalize the cart info for the client? no problem, the view can adapt...
To be honest, it's my view as a programmer but other uses will certainly be found by db gurus :)
One advantage of using an indexed view is for ordering results of 2 or more columns, where the columns are in different tables. ie, have a view which is the result of table1 and table2 sorted by table1.column1, table2.column2. You could then create an index on column1, column2 to optimise that query
A table is where the data is physically stored.
A view is where tables are summarized or grouped to make groups of tables easier to use.
An indexed view allows a query to use a view, and not need to get data from the underlying table, as the view already has the data, thus increasing performance.
You could not achieve the same result with just tables, without denormalizing your database, and thus potentially creating other issues.
Basically, use a view:
When you use the same complex query on many tables, multiple times.
When new system need to read old table data, but doesn't watch to change their perceived schema.
Indexed Views can improve performance by creating more specific index without increasing redundancy.
A view is simply a SELECT statement that has been given a name and stored in a database. The main advantage of a view is that once it's created, it acts like a table for any other SELECT statements that you want to write.
The select statement for the view can reference tables, other views and functions.
You can create an index on the view (indexed view) to improve performance. An indexed view is self-updating, immediately reflecting changes to the underlying tables.
If your indexed view only selects columns from one table, you could just as well place the index on that table and query that table directly, the view would only cause overhead for your database. However, if your SELECT statement covers multiple tables with joins etc. than you could gain a performance boost by placing an index on the view.
I have a SQL Server as backend and use ms access as frontend.
I have two tables (persons and managers), manager is derived from persons (a 1:1 relation), thus i created a view managersFull which is basically a:
SELECT *
FROM `managers` `m`
INNER JOIN `persons` `p`
ON `m`.`id` = `p`.`id`
id in persons is autoincrementing and the primary key, id in managers is the primary key and a foreign key, referencing persons.id
now i want to be able to insert a new dataset with a form in ms access, but i can’t get it to work. no error message, no status line, nothing. the new rows aren’t inserted, and i have to press escape to cancel my changes to get back to design view in ms access.
i’m talking about a managers form and i want to be able to enter manager AND person information at the same time in a single form
my question is now: is it possible what i want to do here? if not, is there a “simple” workaround using after insert triggers or some lines of vba code?
thanks in advance
The problem is that your view is across several tables. If you access multiple tables you could update or insert in only one of them.
Please also check the MSDN for more detailed information on restrictions and on proper strategies for view updates
Assuming ODBC, some things to consider:
make sure you have a timestamp field in the person table, and that it is returned in your managers view. You also probably need the real PK of the person table in the manager view (I'm assuming your view takes the FK used for the self-join and aliases it as the ID field -- I wouldn't do that myself, as it is confusing. Instead, I'd use the real foreign key name in the managers view, and let the PK stand on its own with its real name).
try the Jet/ACE-specific DISTINCTROW predicate in your recordsource. With Jet/ACE back ends, this often makes it possible to insert into both tables when it's otherwise impossible. I don't know for certain if Jet will be smart enough to tell SQL Server to do the right thing, though.
if neither of those things works, change your form to use a recordsource based on your person table, and use a combo box based on the managers view as the control with which you edit the record to relate the person to a manager.
Ilya Kochetov pointed out that you can only update one table, but the work-around would be to apply the updates to the fields on one table and then the other. This solution assumes that the only access you have to these two tables is through this view and that you are not allowed to create a stored procedure to take care of this.
To model and maintain two related tables in access you don’t use a query or view that is a join of both tables. What you do is use a main form, and drop in a sub-form that is based on the child table. If the link master and child setting in the sub-form is set correctly, then you not need to write any code and access will insert the person’s id in the link field.
So, don’t use a joined table here. Simply use a form + sub-form setup and you be able to edit and maintain the data and the data in the related child table.
This means you base the form on the table, and not a view. And you base the sub-form on the child table. So, don't use a view here.