ORACLE日常语句记录

以你之姓@ 2022-09-25 06:18 250阅读 0赞

–asc 按升序排列

select t.amount,ROWNUM from T_STUDENT T order by T.times asc

–desc 按降序排列

select t.amount,ROWNUM from T_STUDENT T order by T.times desc

–类似

select * from T_STUDENT where username like '三%'

–选择多个条件的数据

select * from T_STUDENT  where username in('张三','张三9')

–选择多个条件的数据

select * from T_STUDENT where username in(SELECT username FROM T_STUDENT )

–是空判断

select * from T_STUDENT  where age is null

–非空判断

select * from T_STUDENT where age is not null

–select的查询语句可支持多层

select * from T_STUDENT where (SELECT age FROM T_STUDENT WHERE AGE=78)=AGE

–复制表的结构及数据

create table T_STUDENT as select * from T_STUDENT2

–distinst rows 两个表的数据记录全部合并显示但是去除重select t.username, t.age from T\_STUDENT t  
union  
select t.username, t.age from T\_STUDENT t  
–all rows 两个表的数据记录全部合并显示

select t.username, t.age from T_STUDENT t union all select t.username, t.age from T_STUDENT t

– left join inner join right join 左联结 内联结 右联结  
– left join (左联接) 返回包括左表中的所有记录和右表中联结字段相等的记录  
– right join (右联接) 返回包括右表中的所有记录和左表中联结字段相等的记录  
– inner join (等值连接) 只返回两个表中联结字段相等的行

select t.name,d.pro_name,d.price from USERS t inner JOIN T_ORDER d on d.username_id = t.name
    select t.name,d.pro_name,d.price from USERS t,T_ORDER d
    where d.username_id(+) = t.name

–分页

SELECT * FROM ( SELECT A.*, ROWNUM RN FROM (SELECT * FROM SIXGOD2) A WHERE ROWNUM <= 40 ) WHERE RN >= 1

–分页第二个方式，可以使用between and的方式做分页

SELECT * FROM ( SELECT A.*, ROWNUM RN FROM (SELECT * FROM T_STUDENT) A ) WHERE RN BETWEEN 2 AND 4

–条件取值decode,类似if else，后面可以写多个else

select DECODE(T.AGE,78,'张三78',26,'张三26',t.username), t.age from T_STUDENT t

–条件取值case when，类似If else

select case T.AGE when 78 then '张三78' end from SIXGOD2 t

–生成随机值

select sys_guid() from  dual

–判断是否为空，如果为空就显示第二个参数

select NVL (T.USERNAME_ID, ' IS NULL ') from T_ORDER t