Context: I'm trying to INSERT data in a partitioned table. My table is partitioned by months, because I have lots of data (and a volume expected to increase) and the most recent data is more often queried. Any comment on the partition choice is welcome (but an answer to my question would be more than welcome).
The documentation has a partition example in which, when inserting a line, a trigger is called that checks the new data date and insert it accordingly in the right "child" table. It uses a sequence of IF and ELSIF statements, one for each month. The guy (or gal) maintaining this has to create a new table and update the trigger function every month.
I don't really like this solution. I want to code something that will work perfectly and that I won't need to update every now and then and that will outlive me and my grand-grand-children.
So I was wondering if I could make a trigger that would look like this:
INSERT INTO get_the_appropriate_table_name(NEW.date) VALUES (NEW.*);
Unfortunately all my attempts have failed. I tried using "regclass" stuffs but with no success.
In short, I want to make up a string and use it as a table name. Is that possible?
I was just about to write a trigger function using EXECUTE to insert into a table according to the date_parts of now(), or create it first if it should not exist .. when I found that somebody had already done that for us - right under the chapter of the docs you are referring to yourself:
http://www.postgresql.org/docs/9.0/interactive/ddl-partitioning.html
Scroll all the way down to user "User Comments". Laban Mwangi posted an example.
Update:
The /interactive branch of the Postgres manual has since been removed, links are redirected. So the comment I was referring to is gone. Look to these later, closely related answers for detailed instructions:
INSERT with dynamic table name in trigger function
Table name as a PostgreSQL function parameter
For partitioning, there are better solutions by now, like range partitioning in Postgres 10 or later. Example:
Better database for “keep always the 5 latest entries per ID and delete older”?
Related
I'm a bit of a newbie with the workings of phpmyadmin. I have a database and now there are 2 parts within it - the original tables jos_ and the same again but with a different prefix, say let's ****_ that will be the finished database.
This has come about because I am upgrading my Joomla 1.5 site to 2.5. I used a migration tool for the bulk of the new database but one particular piece of information did not transfer because the new database has a different structure.
I want to copy the entire contents of jos_content, attribs, keyref= across to ****_content, metadata, "xreference"."VALUE" if that makes sense. This will save manually typing in the information contained within 1000s of articles.
jos_content, attribs currently contains
show_title=
link_titles=
show_intro=
show_section=
link_section=
show_category=
link_category=
show_vote=
show_author=
show_create_date=
show_modify_date=
show_pdf_icon=
show_print_icon=
show_email_icon=
language=
keyref=41.126815,0.732623
readmore=
****_content, metadata currently contains
{"robots":"all","author":""}
but I want it to end up like this
{"robots":"","author":"","rights":"","xreference":"41.126815,0.732623","marker":""}
Could anyone tell me the SQL string that I would need to run to achieve this please?
If it makes any difference I have manually changed about 300 of these articles already and thought there must be a better way.
Edit: Being nervous of trying this I would like to try and find the exact syntax (if that's the right word) for the SQL Query to run.
The value I want to extract from the source table is just, and only, the numbers next to keyref= and I want them to turn up in the destination table prefixed by "xreference". - so it shows "xreference"."VALUE" with VALUE being the required numbers. There is also an entry - ,"marker":"" that is in the destination table so I guess the Query needs to produce that as well?
Sorry for labouring this but if I get it wrong, maybe by guessing what to put, I don't really have the knowledge to put it all right again....
Thanks.
Please Try it
insert into tableone(column1,column2) select column1,column2 from Tablesecond
if You have not Table another Daabase Then This query
select * into anyname_Table from tablesource
On a small pre-registration database, I'm using the following SQL to generate a VIEW whenever a specific user name is given. I'm using this mainly to get a snapshot whenever a sysadmin suspects duplicate names are registering. This will be done rarely (atmost once per hour), so the database schema shouldn't be getting excessively big.
CREATE OR REPLACE TRIGGER upd_on_su_entry
AFTER UPDATE OR INSERT
ON PRE_REG_MEMBER
FOR EACH ROW
BEGIN
IF :new.MEMBER_NAME = 'SysAdmin Dup Tester' THEN
EXECUTE IMMEDIATE 'CREATE OR REPLACE VIEW mem_n AS SELECT :old.MEMBER_NAME, COUNT(:old.MEMBER_NAME) FROM MEMBER GROUP BY MEMBER_NAME';
END IF;
END;
However, this appears to be a bloated, inefficient and erroneous way of working (according to my admin). Is there a fundamental error here ? Can I take an equivalent snapshot some other way?
I'm very new to SQL, so please bear with me.
Also, I want to be using the view as :
public void dups()throws Exception
{
Calendar cal = Calendar.getInstance();
jt.setText("Duplicate List at : "+ cal.getTime());
try{
rs=stat.executeQuery("select * from upd_on_su_entry");
while(rs.next())
{
jt.append(rs.getString("MEMBER_NAME")+"\t");
jt.append(rs.getString(2)+"\t");
}
}
catch(Exception e){System.out.print("\n"+e);}
}
There seem to be some misunderstandings here.
1.) views are basically stored sql statements, not stored sql results, so your view will always display the data as it is at the point of querying the view.
2.) Never ever use DDL (create statements) and similar during normal processing of an application. Its just not the way databases are intended to work.
If you want a snapshot at a point in time, create a secondary table which contains all the columns of the original table plus a snapshot time stamp.
When ever you want to make a snapshot copy all the data you want from the original table into the snapshot table while adding the current time stamp.
Based on your comment, it sounds like you want something like this
SELECT MEMBER_NAME FROM PRE_REG_MEMBER
GROUP BY MEMBER_NAME HAVING COUNT(*) > 1;
This will return all members with more than one row in the table
Again, ask yourself "what am I trying to do"?
Don't focus on the technology. Do that after you have a clear idea of what your goal is.
If you are just trying to avoid duplicate registrations on your database, just search the users table and show an error if that username is already there.
Also, think of your datamodel carefully before going into the implementation details.
I'm working on a stored procedure, see my last question that explains what I want.
I've created a sproc that adds a movie to the database, and runs separate sprocs from within to create for example a cast for the movie and adds a genre to it (stored in a separate table).
When running the sproc "NewMovie" a new movie gets added to the database, and the ID of that movie is used in the two other sprocs that I run after the movie is added. The problem is that after for example the cast is created, ##IDENTITY refers to CastID, but I need to use the movie ID again after this.
Is it some way that I can get the next latest created ID, or how could I accomplish what I want?
The code so far can be found here if someone has the time to look through it.
Thanks in advance!
Out of curiosity, you already have #MovieID in usp_NewMovie - why not just use that as a parameter to usp_AddGenre and usp_AddMovieRole?
Also you might be better off using SCOPE_IDENTITY() instead of ##IDENTITY http://blog.sqlauthority.com/2007/03/25/sql-server-identity-vs-scope_identity-vs-ident_current-retrieve-last-inserted-identity-of-record/
I made some updates to your code here: http://pastebin.com/rhhrGsuB
I'm developing an app which requires that the user selects a year formatted like this 1992-1993 from a spinner. The tablename is also named 1992-1993 and the idea is that using SQL the values from this table are pulled through with a statement like this select * from 1992-1993. When I run the emulator however, it throws an error.
If I then relabel the Spinner item to NinetyTwo and rename the table to NinetyTwo and run the emulator it runs as expected and the data is pulled through from the table.
Does SQLite have an issue with numbers in table names?
Yes and No. It has an issue with numbers at the beginning of a table name. 1992-1993 is an expression returning -1. Try to rename the table to Year1992.
Here a similar issue on SO.
sorry for late post
There may be a deeper issue here - is the structure you are using (table name per item in spinner) the best one for the job?
You may find that you want a number of tables e.g.
spinner_value (id, value)
form_data(id, spinner_value_id, etc ....)
What do I gain by adding a timestamp column called recordversion to a table in ms-sql?
You can use that column to make sure your users don't overwrite data from another user.
Lets say user A pulls up record 1 and at the same time user B pulls up record 1. User A edits the record and saves it. 5 minutes later, User B edits the record - but doesn't know about user A's changes. When he saves his changes, you use the recordversion column in your update where clause which will prevent User B from overwriting what User A did. You could detect this invalid condition and throw some kind of data out of date error.
Nothing that I'm aware of, or that Google seems to find quickly.
You con't get anything inherent by using that name for a column. Sure, you can create a column and do the record versioning as described in the next response, but there's nothing special about the column name. You could call the column anything you want and do versioning, and you could call any column RecordVersion and nothing special would happen.
Timestamp is mainly used for replication. I have also used it successfully to determine if the data has been updated since the last feed to the client (when I needed to send a delta feed) and thus pick out only the records which have changed since then. This does require having another table that stores the values of the timestamp (in a varbinary field) at the time you run the report so you can use it compare on the next run.
If you think that timestamp is recording the date or time of the last update, it does not do that, you would need dateTime fields and constraints (To get the orginal datetime)and triggers (to update) to store that information.
Also, keep in mind if you want to keep track of your data, it's a good idea to add these four columns to every table:
CreatedBy(varchar) | CreatedOn(date) | ModifiedBy(varchar) | ModifiedOn(date)
While it doesn't give you full history, it lets you know who and when created an entry, and who and when last modified it. Those 4 columns create pretty powerful tracking abilities without any serious overhead to your DB.
Obviously, you could create a full-blown logging system that tracks every change and gives you full-blown history, but that's not the solution for the issue I think you are proposing.