基本
--新建表: create table table1( id varchar(300) primary key, name varchar(200) not null); --插入数据 insert into table1 (id,name) values ('aa','bb'); --更新数据 update table1 set id = 'bb' where id='cc'; --删除数据 delete from table1 where id ='cc'; --删除表 drop table table1; --修改表名: alter table table1 rename to table2; --表数据复制: insert into table1 (select * from table2); --复制表结构: create table table1 select * from table2 where 1>1; --复制表结构和数据: create table table1 select * from table2; --复制指定字段: create table table1 as select id, name from table2 where 1>1; --条件查询: select id,name (case gender when 0 then '男' when 1 then ‘女’ end ) gender from table1
数学函数
--绝对值:abs() select abs(-2) value from dual; --(2) --取整函数(大):ceil() select ceil(-2.001) value from dual; --(-2) --取整函数(小):floor() select floor(-2.001) value from dual; --(-3) --取整函数(截取):trunc() select trunc(-2.001) value from dual; -- (-2) --四舍五入:round() select round(1.234564,4) value from dual; --(1.2346) --取平方:Power(m,n) select power(4,2) value from dual; --(16) --取平方根:SQRT() select sqrt(16) value from dual; --(4) --取随机数:dbms_random(minvalue,maxvalue) select dbms_random.value() from dual; (默认是0到1之间) select dbms_random.value(2,4) value from dual; (2-4之间随机数) --取符号:Sign() select sign(-3) value from dual; --(-1) select sign(3) value from dual; --(1) --取集合的最大值:greatest(value) select greatest(-1,3,5,7,9) value from dual; --(9) --取集合的最小值:least(value) select least(-1,3,5,7,9) value from dual; --(-1) --处理Null值:nvl(空值,代替值) select nvl(null,10) value from dual; --(10) select nvl(score,10) score from student;
rownum相关
--rownum小于某个数时可以直接作为查询条件(注意oracle不支持select top) select * from student where rownum2; select * from (select rownum rn, student.* from student) where rn >3; --区间查询 select * from (select rownum rn, student.* from student) where rn >3 and rn