| performance issues [message #50495] |
Mon, 18 March 2002 18:16  |
debichowdhuri
Messages: 2
Registered: March 2002
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Junior Member |
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Is there any storage issues if we use a null field in a table. What I mean is it better to use all not null fields in a table rather than to use not null and null fields in a table. Is there some issues of page space swaping due to null and not null. I am working in oracle 9i and trying to design a table for trading system where performance is the main issue. I also wnat to know if using char is better than varchar2 so that you always have fixed length again to avoid any performance issues.
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| Re: performance issues [message #50498 is a reply to message #50495] |
Mon, 18 March 2002 18:45  |
Carnage
Messages: 9
Registered: March 2002
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Junior Member |
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Yes it does matter , as far as possible give not null field first preference and null fields should be placed last. Oracle block header mark the last null values with zero bytes and your row length remain small
Go through block and extents chapter in concept manual
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| Re: performance issues [message #50509 is a reply to message #50495] |
Tue, 19 March 2002 03:16 |
kiran srirama
Messages: 14
Registered: March 2002
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Junior Member |
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Hi..
Its always a good practise to put the columns which may contain NULL values at the last of the CREATE table column list. This will enhance the space management in your database becoz these columns will not be allocated any memory unless they have values in them. If these columns are lying between two NOT NULL columns, Oracle is forced to allocate memory for those NULL columns even is there is no valid data present in them.
Coming to your second Q, i dont think there would be major gain in performance. Only gain is space when you use Varchar2.
Regz..
Kiran
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