发布时间 : 星期三 文章sql语句及案例更新完毕开始阅读701f77561a37f111f0855b67
基本
--新建表:
createtable table1( id varchar(300) primarykey, name varchar(200) notnull);
--插入数据
insertinto table1 (id,name) values ('aa','bb');
--更新数据
update table1 set id ='bb'where id='cc';
--删除数据
deletefrom table1 where id ='cc';
--删除表
droptable table1;
--修改表名:
altertable table1 rename to table2;
--表数据复制:
insertinto table1 (select*from table2);
--复制表结构:
createtable table1 select*from table2 where1>1;
--复制表结构和数据:
createtable table1 select*from table2;
--复制指定字段:
createtable table1 asselect id, name from table2 where1>1;
--条件查询:
select id,name (case gender when0then'男'when1then ‘女’ end ) gender from table1
数学函数
--绝对值:abs()
selectabs(-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()
selectfloor(-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()
selectround(1.234564,4) value from dual; --(1.2346)
--取平方:Power(m,n)
selectpower(4,2) value from dual; --(16)
--取平方根:SQRT()
selectsqrt(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()
selectsign(-3) value from dual; --(-1) selectsign(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 rownum <3;
--查询rownum大于某个数值,需要使用子查询,并且rownum需要有别名 select*from(select rownum rn ,id,name from student) where rn>2; 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 >3and rn<6;
--排序+前n条 select*from (select rownum rn, t.*from ( select d.*from DJDRUVER d orderby drivernumber)t )p where p.rn<10;
--排序+区间查询1 select*from (select rownum rn, t.*from ( select d.*from DJDRIVER d orderby DJDRIVER_DRIVERTIMES)t )p where p.rn<9and p.rn>6;
--排序+区间查询2 select*from (select rownum rn, t.*from ( select d.*from DJDRIVER d orderby DJDRIVER_DRIVERTIMES)t where rownum<9 )p where p.rn>6;--效率远高于方式一
分页查询
(假设每页显示10条) 不包含排序:
--效率低
select*from (select rownum rn, d.*from DJDRIVER d )p where p.rn<=20and p.rn>=10;
select*from (select rownum rn, d.*from DJDRIVER d )p where p.rn between10and20;
--效率高
select*from (select rownum rn, d.*from DJDRIVER d where rownum<=20 )p where p.rn>=10;
包含排序:
--排序+区间查询1(效率低)
select*from (select rownum rn, t.*from ( select d.*from DJDRIVER d orderby DJDRIVER_DRIVERTIMES)t )p where p.rn<=20and p.rn>=10;
select*from (select rownum rn, t.*from ( select d.*from DJDRIVER d orderby DJDRIVER_DRIVERTIMES)t )p where p.rn between10and20;
--排序+区间查询2(效率高)
select*from (select rownum rn, t.*from ( select d.*from DJDRIVER d orderby DJDRIVER_DRIVERTIMES)t where rownum<=20 )p where p.rn>=10;
时间处理
1. to_char和to_date基本使用