SELECT * FROM T1 INNER JOIN T2 ON P1(T1,T2)
INNER JOIN T3 ON P2(T2,T3)
WHERE P(T1,T2,T3).

FOR each row t1 in T1 {
    FOR each row t2 in T2 such that P1(
 
t1,t2) {
        FOR each row t3 in T3 such that P2(t2,t3) {
            IF P(t1,t2,t3) {
                t:=t1||t2||t3; OUTPUT t;
            }
        }
    }
}

FOR each row t1 in T1 {
    IF P(
 
t1) {
        FOR each row t2 in T2 such that P1(t1,t2) {
            IF P(t2) {
                FOR each row t3 in T3 such that P2(t2,t3) {
                    IF P(t3) {
                        t:=t1||t2||t3; OUTPUT t;
                    }
                }
            }
        }
    }
}

FOR each row t1 in T1 {
    IF P(t1) {
        FOR each row t2 in T2 such that (P1(t1,t2) && P(t2)) {
            FOR each row t3 in T3 such that (P2(t2,t3) && P(t3)) {
                t:=t1||t2||t3; OUTPUT t;
            }
        }
    }
}

#include <iostream>
#include <cstdlib>
#include <time.h>
#define MAXN 100000
 
using namespace std;
 
int a[MAXN];
int b[MAXN];
int c[MAXN];
int count = 0;
 
int main() {
	clock_t start, finish;
	double time1, time2;
 
	count = 0;
	srand(time(0));
 
	for(int i=0; i<MAXN; ++i) {
		a[i] = i;
		b[i] = MAXN-i;
		c[i] = rand()%MAXN;
	}
 
	start=clock();
	for(int i=0; i<MAXN; ++i) {
		for(int j=10; j<MAXN; ++j) {
			if (a[i]==b[j]) {
				for(int k=0; k<MAXN; ++k) {
					if(b[j]==c[k]) {
						if (a[i]>500 and b[j] < 800 and c[k]>120) {
							cout << ++count << ':' <<a[i] << ',' << b[j] << ',' << c[k] << endl;
						}
					}
				}
			}
		}
	}
	finish = clock();
	time1 = (double)(finish-start)/CLOCKS_PER_SEC;
 
	count = 0;
	start=clock();
	for(int i=0; i<MAXN; ++i) {
		if (a[i]>500) {
			for(int j=10; j<MAXN; ++j) {
				if (a[i]==b[j] and b[j] < 800) {
					for(int k=0; k<MAXN; ++k) {
						if(b[j]==c[k] and c[k]>120) {
							cout << ++count << ':' <<a[i] << ',' << b[j] << ',' << c[k] << endl;
						}
					}
				}
			}
		}
	}
	finish = clock();
	time2 = (double)(finish-start)/CLOCKS_PER_SEC;
 
	cout << time1 << "VS" << time2 << endl;
	return 0;
}