What is the Fenapoucci sequence? How to create a sequence

In 1150, the Indian mathematicians Gopala and Jin Yue first described this sequence when they studied the number of feasible methods for packing objects in boxes with exactly 1 and 2 in length and width. In the West, Leonardo of Pisa (also known as Fibonasi) was the first to study this sequence, and he used it to describe the number of rabbits growing.

There is a pair of newborn rabbits in the first month.

After the second month, they are able to give birth.

Each fertile pair of rabbits will give birth to a new pair of rabbits every month.

Rabbits never die.

Assuming that there are a total of a pair of newborn and fertile rabbits in month n, there will be a total of b pairs in month n+1. There must be a total of A+B pairs in n+2: because in n+2, all A pairs of rabbits that existed in N+2 are already fertile and give birth to A pairs; At the same time, among the b pairs of rabbits in the previous month (n+1 month), the rabbits that were newly born in that month were not yet able to give birth.

Kepler found that the ratio of two Fibonacci sequences would approach the split.

It's fair to say that the Fibonacci sequence is everywhere, and here are just a few common examples.

1 The sum of the numbers on the diagonal of the Yang Hui triangle forms the Fibonacci sequence

2 dominoes (which can be seen as squares of the size of 2 1) completely cover a board of n 2, covering the number of schemes equal to the Fib sequence.

3 From the point of view of the reproduction of bees, the male peak has only a mother, and no father, because the eggs laid by the queen bee are incubated into females, and the unfertilized ones are hatched into males. When people trace the ancestors of the male peak, they find that the number of the nth generation of ancestors of a male peak is exactly the nth term fn of the Fibonacci sequence.

4 The arrangement of the 13 chromatic scales of the piano is exactly similar to that of the sixth generation of the peak, indicating that the tone is also related to the Fibonacci sequence.

5 The number of petals of some flowers in nature corresponds to the Fibonacci sequence, which means that in most cases, the number of petals of a flower is 3, 5, 8, 13, 21, 34, ,......

6 If a branch grows a new branch every year, and two years after the new branch grows, a new branch grows every year, then the number of branches in the years also constitutes a Fibonacci sequence

1、create sequence

You first need to have the create sequence or create any sequence permission, create sequence emp sequence --emp sequence.

increment by 1 -- add several at a time.

start with 1 -- Count from 1.

nomaxvalue -- the maximum value is not set.

nocycle -- always accumulates, does not cycle.

cache 10;

Once the emp sequence is defined, you can use currval, nextval

currval=Returns the current value of the sequence.

nextval=Increments the value of sequence, then returns the value of sequence.

For example: EMP

emp where you can use sequence:

Select statements that do not contain subqueries, snapshots, and views.

insert statement.

nsertstatement.

update.

You can look at the following example:

insert into emp values, 'lewis', 'clerk',7902, sysdate, 1200, null, 20);

select from dual;

But be careful:

The first nextval returns the initial value; Subsequent nextval will automatically increment the increment by value you define, and then return the increased value. currval always returns the value of the current sequence, but you can't use currval until after the first nextval initialization, otherwise you'll get an error. A nextval increments the value of the sequence, so if you use multiple nextvals in the same statement, the values will be different.

Got it? - If you specify a cache value, oracle can pre-place some sequences in memory so that the access is faster. After the cache is retrieved, Oracle automatically fetches another group to the cache. If you use a cache, you may skip a log, for example, if the database suddenly shuts down (Abort), the sequence in the cache will be lost.

So you can use nocache to prevent this when creating a sequence.

To modify the host file of the computer, block the background network authentication, and then activate it with the cracked registration number.

Routine: Support the Genuine! ）

1045-0502-9715-8471-5218-7925

I've always used this!

If you don't use a serial number, you don't need a serial number here:

Chinese Popular Edition

Simplified version of the game

Serial Number -- Perfect Edition Serial Number ---

It could be 5rp2e-eph3k-br3lg-kmgte-fn8py or 58v2e-cckcj-b8vse-mew9y-acb2k Try it yourself.