Your estimated performance of a very simple SQL query

Hi there..
Sometimes it seems hard to find answers for the most simple questions so I hope you can help me and be overbearing ;)
I am going to have a table with a few million records in it, 30-40 columns of which 80% has data, indexes on maybe 10 columns (certainly the columns I am querying), less than ten thousand new records a day with a variety of different column values and using Oracle 10 or 11.
I am going to be running a single SQL SELECT statement quite regularily against these records to retrieve all records whose value of a single column is the same (and specified in my WHERE clause)
It will be a query like this; SELECT * FROM person where city = 'Amsterdam' AND
The column 'city' will have a simple index on it. 4-8 records will have the same value (e.g. there will only be up to 8 rows where city is 'Amsterdam' in the above example) which means that with 5 million records I will probably have between 625,000 and 1,250,000 "sets" that I am querying and retrieving per SQL. Thed atatype could be varchar or number - not sure yet.
I will retrieve the same data a lot but generally also access all the other data on a regular basis.
How should I expect this to perform? Always fast I imagine because will there will be any table scans do we think? I don't have to think about partitioning of too regular statistic calculation or anything? Anything to watch out for?
Any feedback would be greatly appreciated.
Thanks a lot in advance.
Daniel

It's impossible to tell without seeing a true structure and indexes etc.
It sounds ok at a first read. High selectivity, low cardinality, low skewing. Obviously, ensuring stats are up to date on a reasonably regular basis is a good idea, especially with 10,000+ records added daily. I would expect it to perform ok.

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[email protected]> desc test;
Name                                        Null?    Type
COLUMN1                                              VARCHAR2(20)
COLUMN2                                              VARCHAR2(100)
[email protected]> select count(*) from test;
COUNT(*)
     10000
Elapsed: 00:00:00.00
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Elapsed: 00:00:00.18
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          0 physical reads
          0 redo size
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       7838 bytes received via SQL*Net from client
        668 SQL*Net roundtrips to/from client
          0 sorts (memory)
          0 sorts (disk)
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Elapsed: 00:00:00.18
Execution Plan
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       7838 bytes received via SQL*Net from client
        668 SQL*Net roundtrips to/from client
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          0 redo size
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2 FROM
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13                          WHERE T1.M_ID=MASTER.M_ID
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17                          WHERE T2.M_ID=MASTER.M_ID
18                          ) SRC
19                )
20      ) TS
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It's possible (I already did it) to build a function that returns a dynamix result set from this query build dynamically. I'll let you do so!
Regards,
Yoann.

Simple SQL query

Hi,
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1
1
SQL> select * from ( select 1 from dual, select 2 from dual );
select * from ( select 1 from dual, select 2 from dual )
ERROR at line 1:
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Thanks

user1980 wrote:
Hi,
I would like to know how this type of query is processed internally in Oracle
SQL> select * from ( select 1 from dual, ( select 2 from dual ) g );
1
1
SQL> select * from ( select 1 from dual, select 2 from dual );
select * from ( select 1 from dual, select 2 from dual )
ERROR at line 1:
ORA-00903: invalid table nameWhy would 1 2 not be printed in result?
ThanksJust look at what you are selecting from...
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select 1 from dual, select 2 from dual
ERROR at line 1:
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SQL>it's not valid syntax for an SQL select statement so you can't use it as an inline view.
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Your estimated performance of a very simple SQL query

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