Updatable ResultSet for join Query

Question

Hi all,
It is inevitable that i use a 'JOIN' operation for a particular query and i need the resultSet to be updated. Heard JDBC driver doesnt support this. Is there any workaround for this. Any help is really appreciated.
Thanks,
Abhijit

Answer 1

Welcome to the forum!
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It is inevitable that i use a 'JOIN' operation for a particular query and i need the resultSet to be updated. Heard JDBC driver doesnt support this.
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As gimbal2 mentioned this isn't supported even by the latest 11g version and driver. See 'Result Set Limitations' in Chapter 17 of the JDBC doc for confirmation and discussion.
http://docs.oracle.com/cd/E14072_01/java.112/e10589/resltset.htm#BABBCECI
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Result Set Limitations
The following limitations are placed on queries for enhanced result sets. Failure to follow these guidelines will result in the JDBC driver choosing an alternative result set type or concurrency type.
To produce an updatable result set:
A query can select from only a single table and cannot contain any join operations.
In addition, for inserts to be feasible, the query must select all non-nullable columns and all columns that do not have a default value.
A query cannot use SELECT * .
However, there is a workaround for this.
A query must select table columns only.
It cannot select derived columns or aggregates, such as the SUM or MAX of a set of columns.
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Actually my exact requirement is i have two tables, earlier i used to select the results from one table and check for the existance of the corresponding record in the second table from the output of resultset. This is causing a lot of performance issue and i thought of using a single query by joining two tables which reduces the number of records.
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So is this a correct description of what you want to do?
1. TableA and TableB have one or more columns in common.
2. Query TableA, possibly using filter predicates (WHERE tabA.col1 ...) and identify records in TableB that match on the join columns
3. Update the TableB records from step #2.
If so then you have a couple of options.
The record-by-record approach would be to execute your current query (the one that joins the two tables) but retrieve ONLY the ROWID from TableB. Then iterate thru the result set and use a separate query to get each TableB record by using the ROWID retrieved from the first query. This is different from your original approach because the first query WILL identify the TableB records you need it just won't retrieve them (only the ROWID).
Your original performance issues were probably because you were retrieving ALL of the TableA records and then checking each one to see if there were any TableB records for it.
The BULK approach would be a slight modification of of the record-by-record approach but pushes the work to the DB server.
This approach queries TableB to retrieve ONLY those records that EXIST in the query of TableA just described. So the query is of the form
SELECT * FROM TableB b WHERE EXISTS (SELECT '1' FROM TableA a WHERE a.col1 = b.col1);  This query only uses one table for the resultset and does not contain any join operators so it can be updateable.
Test a simple query first until you get the syntax correct.