Tagged Questions

-2
votes
1answer
49 views

what's the fastest method to export a table through sql query ? 11g - performance

I'm connected to the oracle server remotely. I need to export a table data(the whole table) with millions of records but due the hosting restrictions I can only use SQL (no exp , expdp) . Therefore ...
2
votes
1answer
86 views

Oracle: How to gather stats in a logical standby database?

I have a Primary and a (logical) Standby Database. The Schema 'APP' gets synced. Now a User has performance issues running a query against some tables in this 'APP' schema of the Standby Database. On ...
2
votes
1answer
148 views

oracle merge operation hangs (or loops); query tuner claims it's a cartesian product operation

I have a Merge query (open to better suggestions) that seems to cause the server to hang. (I'm not sure what it's doing, but it pegs the CPU and never completes) When I run it through the query ...
3
votes
3answers
264 views

Why does the query cost change so much and how to prevent it

The query causing me the issue is too big, but the piece that seems to be the core is quite simple, I will try to go with that: The query has an structure like: SELECT ... a lot of stuff ... ...
1
vote
1answer
90 views

What is the best relationship model for high performance?

I want to model a relationship between Customer and Transaction. However, because Customer is only described by a unique string and no extra info, I have two possibilities to implement it in the ...
3
votes
2answers
318 views

Help to understand explain plan in Oracle

I am running a query in some big tables, and although it runs fine even tough is a lot of data, I'd like to understand what part of it weighs on the execution. Unfortunately I am not too good with ...
3
votes
3answers
193 views

optimizing a compare query

Suppose I have two tables, A and B, and I know that size(A) = size(B). I want to confirm that the data in both tables is the same in three given columns, suppose they are X, Y, and Z (there are no ...
0
votes
1answer
92 views

Similar queries taking different times to complete

I had the following query: SELECT nvl(sum(adjust1),0) FROM ( SELECT ManyOperationsOnFieldX adjust1, a, b, c, d, e FROM ( SELECT a, b, c, d, e, SubStr(balance, ...
-3
votes
1answer
215 views

Single query to copy data from 3 tables into a single empty table

In an interview today, I was asked if I could write a single query to copy data from 3 source tables to an empty destination table. I started saying "I will use a temp table or table variables", ...
0
votes
0answers
39 views

Resource to learn writing most efficient and highly optimized sql queries [duplicate]

Possible Duplicate: Learning to Optimize SQL Queries and Understand Execution Plans - Resources? Can some one point me to a great book/great books or some really solid reference/references ...
2
votes
5answers
260 views

Query optimization [Oracle]

The Query: select JOIN_RESULT.batch_id as BATCH_ID, JOIN_RESULT.unique_doc_id as DOCUMENT_ID, JOIN_RESULT.brand as BRAND, JOIN_RESULT.message_date_time as UPLOAD_DATE, ...
2
votes
1answer
298 views

How to calculate query that access system view cost in Oracle?

For a query that returns if there are any active transactions within current session , SELECT COUNT(*) FROM v$transaction t INNER JOIN v$session s ON (t.ses_addr = s.saddr ) INNER ...
0
votes
1answer
95 views

Creating Indexes to optimize query

I have this query and I want to increase its performance by adding appropriate Indexes. DELETE FROM MYTAB1 WHERE MYID1 IN ( SELECT MYID2 FROM MYTAB2 ); I am not familiar with the ...
3
votes
1answer
217 views

Measuring the relative performance of queries given the assertion that “cost” isn't reliable

The cost field is a comparative cost that is used internally to determine the best cost for particular plans. The costs of different statements are not really directly comparable. Source Does ...
3
votes
1answer
132 views

How to search for an ID and its descendants in this query?

I have the following tables: Project Unit ------------- --------------- ID | IDUnit ID | IdParent I have to select all projects that have the IDUnit ...
2
votes
1answer
135 views

Oracle ash report

Recently, i have been handed over with an ash report from DBA. To me this report is like french. I have no idea what it is about and what all is written in this report. Can someone please guide me in ...
1
vote
1answer
176 views

Oracle Benchmarking (SQL_NO_CACHE …)

I want to benchmark some queries on an oracle System from a JDBC application. However, the database seems to cache at some point in time. However, this is not intended in this case. Is there ...