I want to create a view which selects one column from a table.
However, the view select statement will reference two additional columns in its 'where clause'.
The view and the table have different owners.
Is it possible to create the view while only granting 'select' on the one 'desired' column and still allow the query to access the other two columns in it's 'where clause' via a lesser privilege. The idea is to prevent those two columns from being viewed by any other statement which simply included them in its column list.
I'm thinking along the lines of granting 'select' on the 'desired' column and 'references' on the two predicate columns. However, I tried that and it didn't work.
I'm hoping there might be some way of achieving the same?
Related
I have a table with many columns (I know it's not good), but now I want to query the table but only need to group the results by only one of the column, so a general way is:
select table_name.id,
table_name.account_no,
....(all the other column name)
from table_name
where some conditions
group by table_name.bank_name
so I need to write all the other columns for this single query. I'm wondering if there's a better way to do that?
In output I want to select all columns except two columns from a table in q/kdb historical database.
I tried running below query but it does not work on hdb.
delete colid,coltime from table where date=.z.d-1
but it is failing with below error
ERROR: 'par
(trying to update a physically partitioned table)
I referred https://code.kx.com/wiki/Cookbook/ProgrammingIdioms#How_do_I_select_all_the_columns_of_a_table_except_one.3F but no help.
How can we display all columns except for two in kdb historical database?
The reason you are getting par error is due to the fact that it is a partitioned table.
The error is documented here
trying to update a partitioned table
You cannot directly update, delete anything on a partitioned table ( there is a separate db maintenance script for that)
The query you have used as fix is basically selecting the data first in-memory (temporarily) and then deleting the columns, hence it is working.
delete colid,coltime from select from table where date=.z.d-1
You can try the following functional form :
c:cols[t] except `p
?[t;enlist(=;`date;2015.01.01) ;0b;c!c]
Could try a functional select:
?[table;enlist(=;`date;.z.d);0b;{x!x}cols[table]except`colid`coltime]
Here the last argument is a dictionary of column name to column title, which tells the query what to extract. Instead of deleting the columns you specified this selects all but those two, which is the same query more or less.
To see what the functional form of a query is you can run something like:
parse"select colid,coltime from table where date=.z.d"
And it will output the arguments to the functional select.
You can read more on functional selects at code.kx.com.
Only select queries work on partitioned tables, which you resolved by structuring your query where you first selected the table into memory, then deleted the columns you did not want.
If you have a large number of columns and don't want to create a bulky select query you could use a functional select.
?[table;();0b;{x!x}((cols table) except `colid`coltime)]
And show all columns except a subset of columns. The column clause expects a dictionary hence I am using the function {x!x} to convert my list to a dictionary. See more information here
https://code.kx.com/q/ref/funsql/
As nyi mentioned, if you want to permanently delete columns from an historical database you can use the deleteCol function in the dbmaint tools https://github.com/KxSystems/kdb/blob/master/utils/dbmaint.md
In a PostgreSQL db I'm working on, half of the tables have one particular column, always named the same, that is of type varchar(5). The size became a bit too restricting and I want to change it to varchar(10).
The number of tables in my particular case is actually very manageable to do it by hand. But I was wondering how one could script this with a query for larger dbs. It generally should be possible in just a few steps.
Identify all the tables in the schema, then (?) filter by condition if column present.
Create ALTER TABLE statements for each table found
I have some idea about how to write a query that identifies all tables in the schema. But I wouldn't know how to filter them. And if I didn't filter them, I assume the generated alter table statements would break.
Would be great if someone could share their knowledge on this.
Thanks to Abelisto for providing some guidance. Eventually, this is how I did it.
First, I created a query that in turn creates the ALTER TABLE statements. MyDB and MyColumn need to reflect actual values.
SELECT
'ALTER TABLE '||columns.table_name||' ALTER COLUMN '||MyColumn||' TYPE varchar(20);'
FROM
information_schema.columns
WHERE
columns.table_catalog = 'MyDB' AND
columns.table_schema = 'public' AND
columns.column_name = 'MyColumn';
Then it was just a matter of executing the output as a new query. All done.
I have to display a column name from a select query from table, e,g, 'Column 1' is stored in table table1, I want to display 'Column 1' as column name. I cannot hardcode 'Column 1' as it might be unknown when the code is developed.
Column 1 Column 2
a b
Any idea?
Update
It allows user to define column name.
It has to generate via T SQL
Add alias as a separate column or use dynamic SQL
This doesn't make sense because doing you should know what the column is called: you don't store information about columns and build queries on your own metadata
IF you don't know the name of the column at design time, then use a resource file or similar in the presentation layer to hold the value that you will display as the label for column1. It should be noted, however, you are going to have a very hard time writing any code if you don't know the names of the columns in your database, unless you are select * on everything.
Column names are fairly restricted and should be named with the SQL admin and application developer as the user of the names. It is not the intent of a column name to be descriptor for the end user interface.
Select dbColumn1 as [Customer Name] from tableMain
Even that is not a good practice and then user input is part of the TSQL and you are opening yourself up to SQL injection attacks and it is just not very good control on you query. A better practice is to pass parameters.
Oh helloes!
I have two tables, first one (let's call it NameTable) is preset with a set of values (id, name) and the second one (ListTable) is empty but with same columns.
The question is: How can I insert into ListTable a value that comes from NameTable? So that if I change one name in the NameTable then automagically the values in ListTable are updated aswell.
Is there INSERT for this or does the tables has to be created in some special manner?
Tried browsing the manual but without success :(
The suggestion for using INSERT...SELECT is the best method for moving between tables in the same database.
However, there's another way to deal with the auto-update requirement.
It sounds like these are your criteria:
Table A is defined with columns (x,y)
(x,y) is unique
Table B is also defined with columns (x,y)
Table A is a superset of Table B
Table B is to be loaded with data from Table A and needs to remain in sync with UPDATEs on Table A.
This is a job for a FOREIGN KEY with the option ON UPDATE CASCADE:
ALTER TABLE B ADD FOREIGN KEY (x,y) REFERENCES A (x,y) ON UPDATE CASCADE;
Now, not only will it auto-update Table B when Table A is updated, table B is protected against containing (x,y) pairs that do not exist in Table A. If you want records to auto-delete from Table B when deleted from Table A, add "ON UPDATE DELETE."
Hmmm... I'm a bit confused about exactly what you want to do or why, but here are a couple of pointers towards things you might want to take a look at: table inheritance, triggers and rules.
Table inheritance in postgresql allows a table to share the data of a another table. So, if you add a row to the base table, it won't show up in the inherited table, but if you add a row to the inherited table, it will now show up in both tables and updates in either place will reflect it in both tables.
Triggers allow you to setup code that will be run when insert, update or delete operations happen on a table. This would allow you to add the behavior you describe manually.
Rules allow you to setup a rule that will replace a matching query with an alternative query when a specific condition is met.
If you describe your problem further as in why you want this behavior, it might be easier to suggest the right way to go about things :-)