Foreign key benefits of memory consumption

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Please tell me the benefit of creating foreign key. Let me first explain my question

Suppose we have a table called "SonogrpahyReport" which need to store "patientid", and "Report" fields. "Report" field contains actual word document which might have size of 1.2 MB or something. Most of the patients have normal report with same word in report.

If I create the table Master_Report_data which contain a report and make a foreign key between "SonogrpahyReport" and "Master_Report_data" with a column report then can report data be stored at a one place (only in Master_Report_data ) and its address store in (report column of SonogrpahyReport).

So if I have 5 patients with normal report then only 1.2 MB of memory consume by data. Is this the scenario with foreign key?

Posted 1-Nov-10 2:45am

RDBurmon

Updated 1-Nov-10 2:59am

HimanshuJoshi

v2

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2 solutions

Solution 1

Normally you'd use a 32 bit integer as a foreign key, which measures 4 bytes. If you had 5 patients, then you'd be using 1258311 bytes instead of 1258291 bytes.

There is virtually no cost to the key.

Cheers.

Posted 1-Nov-10 9:39am

TheyCallMeMrJames

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RDBurmon 2-Nov-10 2:44am

thks for the ans but my Q is

"If I create the table Master_Report_data which contain a report and make a foreign key between "SonogrpahyReport" and "Master_Report_data" with a column report then can report data be stored at a one place (only in Master_Report_data ) and its address store in (report column of SonogrpahyReport).

So if I have 5 patients with normal report then only 1.2 MB of memory consume by data. Is this the scenario with foreign key? "

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AspDotNetDev · Accepted Answer · 2010-11-01T10:05:00

Solution 2

That is called a "one to many relationship". For every report, you may have many patients that it relates to.

In the context of SQL Server, a "foreign key" usually refers to a "foreign key constraint", which dictates that one field in one row on a table must point to a matching field in a row in another table.

Having foreign keys ensures database consistency (e.g., it makes it impossible to have a patient that links to an invalid report).

Posted 1-Nov-10 10:05am

AspDotNetDev

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RDBurmon 2-Nov-10 2:43am

ya this is on the part of data constraint but i am asking is there any such purpose of key so that it eat less space in memroy.

that why here i put the Q like :

"If I create the table Master_Report_data which contain a report and make a foreign key between "SonogrpahyReport" and "Master_Report_data" with a column report then can report data be stored at a one place (only in Master_Report_data ) and its address store in (report column of SonogrpahyReport).

So if I have 5 patients with normal report then only 1.2 MB of memory consume by data. Is this the scenario with foreign key? "

AspDotNetDev 2-Nov-10 17:42pm

You can save memory by storing a large amount of data once and referring to it with a small amount of data several times (rather than storing that large amount of data multiple times), obviously. Creating a foreign key constraint should have no effect on memory.

RDBurmon 6-Nov-10 5:21am

Thanks Frnds.