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AQA A2 COMP 3 Computing 2015 - Official Thread

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Original post by HugeBicepLAD
75 in comp4 looking 100 in comp3 you are all noobs


Someone watches to much Star-Trek and plays too much computer games #Nerd
Original post by HugeBicepLAD
75 in comp4 looking 100 in comp3 you are all noobs


Bad troll is bad. HugeBicepLAD/10. Topkek.
Do we need to know how to INSERT a new field into a table? For example:
https://en.wikibooks.org/wiki/A-level_Computing/AQA/Problem_Solving,_Programming,_Operating_Systems,_Databases_and_Networking/Databases/INSERT

Would we ever get asked to insert, for example, "numCrimes" as a new field? If so, how would we do it?
Reply 263
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Original post by Shaney96
Do we need to know how to INSERT a new field into a table? For example:
https://en.wikibooks.org/wiki/A-level_Computing/AQA/Problem_Solving,_Programming,_Operating_Systems,_Databases_and_Networking/Databases/INSERT

Would we ever get asked to insert, for example, "numCrimes" as a new field? If so, how would we do it?


Is in the syllabus so yeah they could ask that.

I think everyone who did a program that used a database for Comp4 should be fluent in SQL. I don't see why ya'll can't get full marks on the SQL section. The SQL and Programming Concepts section is my favorite parts of the exam :biggrin:
Original post by Shaney96
Do we need to know how to INSERT a new field into a table? For example:
https://en.wikibooks.org/wiki/A-level_Computing/AQA/Problem_Solving,_Programming,_Operating_Systems,_Databases_and_Networking/Databases/INSERT

Would we ever get asked to insert, for example, "numCrimes" as a new field? If so, how would we do it?


Inserting:
Insert INTO <Fieldname>
Values (<values>)

Selecting:
SELECT <fieldname>
FROM<Table>
WHERE <conditions>
Order by <fieldname> asc/desc

Deleting:
DELETE FROM <tablename>
Where<Conditions>

updating:
update <tablename>
set <newValue>
Where <conditions>

Creating:
Create table <tablename>
<fieldname1> <type1>
<fieldname2><type2>
...

I believe that this is the only SQL we should know, although it is from memory and not 100% sure if all command words are correct.
Hope this helps
Original post by Jordancollins1
Inserting:
Insert INTO <Fieldname>
Values (<values>:wink:

Selecting:
SELECT <fieldname>
FROM<Table>
WHERE <conditions>
Order by <fieldname> asc/desc

Deleting:
DELETE FROM <tablename>
Where<Conditions>

updating:
update <tablename>
set <newValue>
Where <conditions>

Creating:
Create table <tablename>
<fieldname1> <type1>
<fieldname2><type2>
...

I believe that this is the only SQL we should know, although it is from memory and not 100% sure if all command words are correct.
Hope this helps


Yeah I know that stuff, I think that'll be sufficient for the exam. Thanks for your time in making this post, I appreciate it and I'm sure others do as well.
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Original post by Jordancollins1
X


They also expect you to be aware of what an ALTER , TRUNCATE/DROP statements do too.

Plus the SELECT statements they ask is never simply. They normally require you to link from multiple tables which makes things harder.
(edited 8 years ago)
I believe I've found what I'm looking for. I think it's something like:

ALTER TABLE <table> ADD <field> <type>

and to remove:

ALTER TABLE <table> DROP COLUMN <field>

Of course I know this as I'm taking notes from WikiBooks and have just got onto this section... Just thought it would be helpful for others. The "COLUMN" shows that you're not destroying the entire table. To do this, just use the "DROP TABLE" command instead, followed by the table name.

Hope this helps anyone.
Original post by BaronK
Overflow is when a number is too large to be represented in the given number of bits.
Underflow is when a number is too small to be represented in the given number of bits.


Good reading there :rolleyes:
Original post by WaterfallM
Overflow may occur when 2 very large numbers are multiplied together, underflow may occur when a very small number is divided by a very large number.


But in 2014 they said overflow occurs when dividing a large number by a very small number...
Reply 270
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BaronK
9
Original post by AlecRobertson
But in 2014 they said overflow occurs when dividing a large number by a very small number...


They both give you larger numbers
(edited 8 years ago)
Original post by AlecRobertson
But in 2014 they said overflow occurs when dividing a large number by a very small number...


Both situations would cause the number to be too large to be represented in the given number of bits
Original post by BaronK
They both give you larger numbers


Wait so just confirm, you get overflow by multiplying large numbers together - do they have to be large or is it just multiplying?
Reply 273
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BaronK
9
Original post by AlecRobertson
Wait so just confirm, you get overflow by multiplying large numbers together - do they have to be large or is it just multiplying?


It's all relative to the number of bits you have in the mantissa and exponent. i.e. if you had only a 4 point floating point number, 2M/2E, then 10*10 would give you overflow.
Multiplying two large numbers or dividing a large number by a much smaller one both give you much larger answers.
Original post by AlecRobertson
Wait so just confirm, you get overflow by multiplying large numbers together - do they have to be large or is it just multiplying?


Yes you do, and yes they have to be large.

Say our really crappy computer only had enough bits to store the number 1000 (our very large number) then we multiplied it by another very large number, in this case 999, the answer, 999000 is too large to be stored in the given number of bits as the largest number we can store is 1000.

Hope that clears it up a little :smile:
Original post by WaterfallM
Yes you do, and yes they have to be large.

Say our really crappy computer only had enough bits to store the number 1000 (our very large number) then we multiplied it by another very large number, in this case 999, the answer, 999000 is too large to be stored in the given number of bits as the largest number we can store is 1000.

Hope that clears it up a little :smile:


That's excellent! :smile:

Can you give a numerical example of dividing too?

Are those the only two situations that result in overflow?
can anybody please link me the specimen paper and markscheme for comp3? i cannot find it anywhere
I have FP2 tomorrow, which makes revising for this a little more interesting :s
Original post by AlecRobertson
That's excellent! :smile:

Can you give a numerical example of dividing too?

Are those the only two situations that result in overflow?


Sure, for dividing, say again the max number we can store is 1000, so we take a very large number, 999, and divide it by a very small number, 0.123, this gives us an answer of 8121.95122, which again is larger than 1000.

I'm not sure of any other instances that will cause an overflow error but those two should be sufficient!
Original post by sarcasmrules
I have FP2 tomorrow, which makes revising for this a little more interesting :s


Mechanics 2 tomorrow...
I've literally only had 4 days worth of revision for COMP3... :s-smilie:
*gulp*

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