--隨機取100條資料從pucentp表中；
select * from (select * from pucentp order
by trunc(dbms_random.random())) where
1=1and rownum<= 100;
select * from (select * from pucentp order
by trunc(dbms_random.value())) where
1=1and rownum<= 100;
dbms_random.value()比dbms_random.random()提取資料速度要快，一般用前者；
--從pucentp表中抽取20%的資料然後從20%的資料中隨機抽取5條資料；
select * from pucentp sample (20) where rownum <= 5;
select * from pucentp sample block (20) where rownum <= 5;
select * from pucentp sample (20) seed(3) where rownum <= 5;
select * from pucentp sample block (20) seed(11) where rownum <= 5;
select to_char(currentdate,'yyyy') currentyear,count(id) sss from pucship where ( to_number(to_char(sysdate,'yyyy')) - to_number(to_char(currentdate,'yyyy')) ) <= 4
group
by to_char(currentdate,'yyyy') order
by to_number(to_char(currentdate,'yyyy')) asc;
--currentdate為表中已經存在的日期字段，然後根據當前年份從你表中（匹配）近5年的資料
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