PLSQL Printing prime numbers - sql

Question

I want to print prime numbers between 1 to 50. But I don't understand what I am doing wrong in my code. After BEGIN, SQLDeveloper says I had an error because it expected another sign and not = .
SET SERVEROUTPUT ON
DECLARE
i NUMBER;
counter NUMBER;
n NUMBER;
k NUMBER;
BEGIN
i := 2;
counter := 0;
n := 50;
k := n/2;
FOR i IN 1..k LOOP
IF (n%i := 0 ) THEN
counter := 1;
END IF;
IF (counter := 0) THEN
DBMS_OUTPUT.PUT_LINE(n||' is prime number');
END IF;
END LOOP;
END;

Answer 1

SET SERVEROUTPUT ON
DECLARE
i NUMBER;
counter NUMBER;
n NUMBER;
k NUMBER;
BEGIN
i := 2;
counter := 0;
n := 50;
k := floor(n/2);
FOR i IN 1..k LOOP
IF (mod(n, i) = 0 ) THEN
counter := 1;
END IF;
IF (counter = 0) THEN
DBMS_OUTPUT.PUT_LINE(n||' is prime number');
END IF;
END LOOP;
END;
k := n/2; -- added FLOOR (k is NUMBER, by default it's NUMBER(38, max_scale))
IF (n%i := 0 ) THEN -> IF (mod(n, i) = 0 ) THEN
Oracle has MOD function for remainder + to compare you need to use =,
:= is for assignment.
DECLARE
counter NUMBER;
k NUMBER;
BEGIN
FOR n IN 1..50 LOOP
counter := 0;
k := floor(n/2);
FOR i IN 2..k LOOP
IF (mod(n, i) = 0 ) THEN
counter := 1;
END IF;
END LOOP;
IF (counter = 0) THEN
DBMS_OUTPUT.PUT_LINE(n||' is prime number');
END IF;
END LOOP;
END;

Answer 2

In your IF clause you are assigning the value instead of comparison. You are using := operator, where you shd be using =
It shud be like (IF counter = 0) then
......
Also I dont think n%i would work, you could do IF (trunc(n) = n) then ... or IF (mod (n,i) =0) then ...

Answer 3

--this function is check prime number.
create or replace function prime_a(x number) return
varchar2 is
n integer;
ans varchar2(50);
begin
n:=(x/2);
for i in 2..n loop
if mod(x,i)=0
then ans:='not a prime';
exit;
else ans:='prime';
end if;
end loop;
return ans;
end;
/

Answer 4

step-1:
create table tob(prime number);
step-2:
create or replace procedure ro(m number,n number)
is
a integer;
co Boolean;
begin
for j in m..n loop
co:=false;
co:=(j=1 );
a:=(j/2);
for i in 2..a loop
co:=(mod(j,i)=0);
exit when co;
end loop;
if(not co) then
insert into tob values(J);
end if;
end loop;
commit;
end;
/
step-3:
exec ro(1,50);
step-4: check:-
select * from tob;

Answer 5

You should create or replace in your source code:
function prime_a(x number) return
varchar2 is
n integer;
ans varchar2(50);
begin
n:=(x/2);
for i in 2..n loop
if mod(x,i)=0
then ans:='not a prime';
exit;
else ans:='prime';
end if;
end loop;
return ans;
end;
/

Answer 6

Why don't you just check for previous prime divisibility?
create table prime (primeno bigint)
declare #counter bigint
set #counter = 2
while #counter < 1000000
begin
if not exists(select top 1 primeno from prime where #counter % primeno = 0)
insert into prime select #counter
set #counter = #counter + 1
end
select * from prime order by 1
You could certainly cap the numbers you are checking against in the where condition to reduce your overheads further.

Answer 7

declare
i number;
j number;
k number:=0;
begin
for i in 1..50
loop
for j in 2..i-1
loop
if mod(i,j)=0 then
k:=1;
exit;
end if;
end loop;
if k=0 then
dbms_output.put_line(i);
end if;
k:=0;
end loop;
end;
/

Answer 8

create or replace function prime_a(x number) return varchar2 is
n integer;
ans varchar2(50);
begin
n:=(x/2);
for i in 2..n loop
if mod(x,i)=0 then
ans:='not a prime';
exit;
else
ans:='prime';
end if;
end loop;
return ans;
end;
/