使用达梦数据库快速查找1000以内的质数

Posted 2023-02-03 El Shaddai.plus

使用达梦数据库快速查找1000以内的质数

• 使用达梦数据库快速查找1000以内的质数
• • SQL语句

使用达梦数据库快速查找1000以内的质数

想找300左右的质数，无意中在网上偶得一个sql，记录一下。

SQL语句

SELECT WM_CONCAT(RN) FROM(
SELECT RN FROM (
WITH T AS
 (SELECT ROWNUM RN FROM DUAL CONNECT BY LEVEL <= 1000)  --使用WITH获取存放1-1000整数的视图T
SELECT TA.RN
  FROM T TA
 WHERE TA.RN > 1                                            --2-1000的整数
MINUS                                                    --差集
SELECT TB.RN * TC.RN                                     
  FROM T TB, T TC
 WHERE TB.RN <= TC.RN AND TB.RN > 1 AND TC.RN > 1 )ORDER BY RN );       --笛卡尔乘积，此时的结果表示因数大于2个的所有数 ，即：2-1000的两个数随机相乘

结果

2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,281,283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,389,397,401,409,419,421,431,433,439,443,449,457,461,463,467,479,487,491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,607,613,617,619,631,641,643,647,653,659,661,673,677,683,691,701,709,719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,829,839,853,857,859,863,877,881,883,887,907,911,919,929,937,941,947,953,967,971,977,983,991,997