| two-dimensional pl/sql table [message #370315] |
Sun, 22 August 1999 13:54  |
Alex
Messages: 190
Registered: August 1999
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Senior Member |
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How can i create a two-dimensional pl/sql table for retrieving, say, student id and courses for that student.
Any help would be greatly appreciated
Alex
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| Re: two-dimensional pl/sql table [message #370328 is a reply to message #370315] |
Fri, 27 August 1999 06:02  |
Chris Hunt
Messages: 27
Registered: March 1999
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Junior Member |
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Unfortunately PL/SQL tables cannot be built with more than one dimension. However, a good thing about them is that they are designed to be "sparse", i.e. a table with two rows numbered 1 and 1000 takes up no more room than one numbered 1 and 2. We can use this fact to simulate a multi-dimensional table.
Say you're confident that no student will do more than 99 courses (or 9 or 999 or whatever), you can generate a single-dimensional index thus:
<CENTER>(student_number * 100) + course_number</CENTER>
so your notional my_table(10,1) would become actual my_table(1001).
Whenever I've done this myself I've written a couple of local procedures/functions to manipulate the table:
<CENTER>FUNCTION get_record(index1,index2,...)
PROCEDURE put_record(index1,index2,...,record)</CENTER>
That way I keep the code for implementing a multi-dimensional table separate from the main code of the package. It's less confusing for subsequent maintenance and means I can change it easily if someone takes more than 99 courses or Oracle implement multi-dimensional arrays in a future version of PL/SQL.
Let me know if you need any more help in this area, I should be able to dig out some example code.
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