I am writing a simple program to insert rows into a table.But when i started writing the program i got a doubt. In my program i will get duplicate input some times. That time i have to notify the user that this already exists.
Which of the Following Approaches is good to Use to achieve this
Directly Perform Insert statement will get the primary key violation error if it is duplicate notify otherwise it will be inserted. One Query to Perform
First make a search for the primary key values. If found a Value Prompt User. Otherwise perform insert operation.For a non-duplicate row this approach takes 2 queries.
Please let me know trade-offs between these approaches. Which one is best to follow ?
Regards,
Sunny.
I would choose the 2nd approach.
The first one would cause an exception to be thrown which is known to be very expensive...
The 2nd approach would use a SELECT count(*) FROM mytable WHERE key = userinput which will be very fast and the INSERT statement for which you can use the same DB connection object (assuming OO ;) ).
Using prepared statements will pre-optimize the queries and I think that will make the 2nd approach much better and mre flexible than the first one.
EDIT: depending on your DBMS you can also use a if not exists clause
EDIT2: I think Java would throw a SQLExcpetion no matter what went wrong, i.e. using the 1st approach you wouldn't be able to differ between a duplicate entry or an unavailable database without having to parse the error message - which is again a point for using SELECT+INSERT (or if not exists)
Related
data source adapter error: java.sql.SQLSyntaxErrorException: ORA-01795: maximum number of expressions in a list is 1000
I am getting this error in cognos.Basically I am working on report enhancement in cognos.I already have searched for solution on internet but provided solution is for oracle, i want solution to be in cognos as i am unable to access database or framework manager. Please let me know what should be the right approch to resolve that error.
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I already have searched for solution on internet but provided solution is for oracle. I want the solution to be in cognos as i am unable to access database or framework manager.
Error you got is indeed raised by Oracle, but the question is whether it should be fixed in Oracle or elsewhere (Cognos?).
Generally speaking, this is what happened:
select whatever from some_table
where id in (1, 2, 3) --> this is the IN clause. In Oracle, it is limited
to 1000 elements
I guess that nobody literally types 1000+ elements into the IN list, but some dynamic piece of code might, concatenating value after value until you reach and pass the limit.
I don't know Cognos, but - if that's what really happens, a simple and effective option is to store values which are being used in IN list into a table, and then either JOIN that table to other table(s), or use it as a subquery.
For example:
select whatever from some_table
where id in (select id from a_new_table)
or
select whatever
from some_table a join a_new_table b on a.id = b.id
Presumably the filter is coming from a prompt and someone is selecting everything in the list in the prompt or close to it.
It might be a good idea to try to figure out why there are so many things being chosen. This would require investigation about the business purpose of the prompt.
It might be that our someone needs to see everything so the prompt should be set as optional, which would not generate the where predicate in the SQL.
It might be that the prompt needs to be generated on an attribute (column) which is at a higher grain of dimensional abstraction (i.e. countries rather than cities).
Simply being told fix it in Cognos is not a very helpful instruction and you need to approach the problem with a better understanding of the purpose of the report.
I have this situation. Starting from a table, I have to check all the records that match a key. If records are found, I have to check another table using a key from the first table and so on, more on less on five levels. There is a way to do this in a recursive way, or I have to write all the code "by hand"? The language I am using is Visual Fox Pro. If this is is not possible, is it al least possible to use recursion to popolate a treeview?
You can set a relation between tables. For example:
USE table_1.dbf IN 0 SHARED
USE table_2.dbf IN 0 SHARED
SET ORDER TO TAG key_field OF table_2.cdx IN table_2
SET RELATION TO key_field INTO table_2 ADDITIVE IN table_1
First two commands open table_1 and table_2. Then you have to set the order/index of table_2. If you don't have an index for the key field then this will not work. The final command sets the relation between the two tables on the key field.
From here you can browse both tables and table_2's records will be filtered based on table_1's key field. Hope this helps.
If the tables have similar structure or you only need to look at a few fields, you could write a recursive routine that receives the name of the table, the key to check, and perhaps the fields you need to check as parameters. The tricky part, I guess, is knowing what to pass down to the next call.
I don't think I can offer any more advice without at least seeing some table structures.
Sorry for answering so late, but the problem was of course that the recursion wasn't a viable solution since I had to search inside multiple tables. So I resolved by doing a simple 2-Level search in the tables that I needed.
Thank you very much for the help, and sorry again for answering so late.
I want to read from a table, change a couple column values for a few lines in a query, then update those lines on the same table.
I'm using SAP BODS, and that's what I tried:
I was about to insert images but just found out I can't insert images until 10 rep.
Anyway, I created a DataFlow where I have the same table as source and target.
A query to filter (using where) and change values (using mapping). And then a Table Comparison (where I expected those lines to be set to update, in this particular case), set table name on first entry, then PK in 'input primary key' and then the two columns I want to change in 'Compare columns'. No other changes from default that I can recall.
Got no warnings on 'validate all', and on execution I receive an ORA-00001 for the PK.
So ... I thought the Table Comparison would try to update, but seems like it's trying to insert instead. I want to know what I'm doing wrong and how could I get the job to do those updates. Thanks in advance.
Ps. I did search SO before asking and didn't find anything relevant.
Ok
So, turns out I just found what's going on a few minutes after posting the question.
Wasn't sure if I should answer my own question and took a look at this Etiquette for answering your own question
and decided to come back here and answer my own question.
For some reason I got stuck thinking that it was something to do with the Table Comparison trying to insert a line with a PK that's already there, instead of doing the update I wanted.
But after going back to the job to take another look at the issue, it occurred to me that maybe the problem could be a duplicate in the incoming data set. Made a few adjustment to filter those, and voilà.
I have a Pesky SSRS report Problem where in the main query of my report has a condition that can have more than 1000 choices and when user selects all it will fail as my backend database is Oracle. I have done some research and found a solution that would work.
Solution is
re-writing the in clause something like this
(1,ColumnName) in ((1,Searchitem1),(1,SearchItem2))
this will work however when I do this
(1,ColumnName) in ((1,:assignedValue))
and pass just one value it works. But when I pass more than one value it fails and gives me ORA-01722: Invalid number error
I have tried multiple combination of the same in clause but nothing is working
any help is appreciated...
Wild guess: your :assignedValue is a comma-separated list of numbers, and Oracle tries to parse it as a single number.
Passing multiple values as a single value for an IN query is (almost) never a good idea - either you have to use string concatenation (prone to SQL injection and terrible performance), or you have to have a fixed number of arguments to IN (which generally is not what you want).
I'd suggest you
INSERT your search items into a temporary table
use a JOIN with this search table in your SELECT
I'm using ASP.NET MVC3 and Entity Framework with Database first aproach.
I have a table with id(key), number and description columns. I need to generate a number after item insertion. I created instead of trigger where I generate number that I need (it depends on last number that allready exists in database).
The problem is: When users insert items at same time the number in both cases is the same. So for both inserted items trigger fires and inside the trigger select returns same last number of item that allready exsist.
What is the best practice to solve this kind of issue?
Thanks.
I believe this will help you.
http://www.sqlteam.com/article/custom-auto-generated-sequences-with-sql-server
Also, if you're using SQL Server 2012, there is a new feature called SQL Sequence. It's something that Oracle databases have for a long time.
If you need those numbers without any gap, I'd suggest you to lock the table (prevent write), query it, update the row with max(number) and unlock it.