网络收集:PLSQL常用方法汇总
文章作者 100test 发表时间 2007:08:06 13:21:19
来源 100Test.Com百考试题网
在SQLPLUS下,实现中-英字符集转换
alter session set nls_language= AMERICAN .
alter session set nls_language= SIMPLIFIED CHINESE .
主要知识点:
一、有关表的操作
1)建表
create table test as 0select * from dept. --从已知表复制数据和结构
create table test as 0select * from dept where 1=2. --从已知表复制结构但不包括数据
2)插入数据:
insert into test 0select * from dept.
二、运算符
算术运算符: - * / 可以在0select 语句中使用
连接运算符:|| 0select deptno|| dname from dept.
比较运算符:> >= = != < <= like between is null in
逻辑运算符:not and or
集合运算符: intersect ,union, union all, minus
要求:对应集合的列数和数据类型相同
查询中不能包含long 列
列的标签是第一个集合的标签
使用order by时,必须使用位置序号,不能使用列名
例:集合运算符的使用:
intersect ,union, union all, minus
0select * from emp intersect 0select * from emp where deptno=10 .
0select * from emp minus 0select * from emp where deptno=10.
0select * from emp where deptno=10 union 0select * from emp where deptno in (10,20). --不包括重复行
0select * from emp where deptno=10 union all 0select * from emp where deptno in (10,20). --包括重复行
三,常用 ORACLE 函数
sysdate为系统日期 dual为虚表
一)日期函数[重点掌握前四个日期函数]
1,add_months[返回日期加(减)指定月份后(前)的日期]
0select sysdate S1,add_months(sysdate,10) S2,
add_months(sysdate,5) S3 from dual.
2,last_day [返回该月最后一天的日期]
0select last_day(sysdate) from dual.
3,months_between[返回日期之间的月份数]
0select sysdate S1, months_between( 1-4月-04 ,sysdate) S2,
months_between( 1-4月-04 , 1-2月-04 ) S3 from dual
4,next_day(d,day): 返回下个星期的日期,day为1-7或星期日-星期六,1表示星期日
0select sysdate S1,next_day(sysdate,1) S2,
next_day(sysdate, 星期日 ) S3 FROM DUAL
5,round[舍入到最接近的日期](day:舍入到最接近的星期日)
0select sysdate S1,
round(sysdate) S2 ,
round(sysdate, year ) YEAR,
round(sysdate, month ) MONTH ,
round(sysdate, day ) DAY from dual
6,trunc[截断到最接近的日期]
0select sysdate S1,
trunc(sysdate) S2,
trunc(sysdate, year ) YEAR,
trunc(sysdate, month ) MONTH ,
trunc(sysdate, day ) DAY from dual
7,返回日期列表中最晚日期
0select greatest( 01-1月-04 , 04-1月-04 , 10-2月-04 ) from dual
二)字符函数(可用于字面字符或数据库列)
1,字符串截取
0select substr( abcdef ,1,3) from dual
2,查找子串位置
0select instr( abcfdgfdhd , fd ) from dual
3,字符串连接
0select HELLO || hello world from dual.
4, 1)去掉字符串中的空格
0select ltrim( abc ) s1,
rtrim( zhang ) s2,
trim( zhang ) s3 from dual
2)去掉前导和后缀
0select trim(leading 9 from 9998767999) s1,
trim(trailing 9 from 9998767999) s2,
trim(9 from 9998767999) s3 from dual.
5,返回字符串首字母的Ascii值
0select ascii( a ) from dual
6,返回ascii值对应的字母
0select chr(97) from dual
7,计算字符串长度
0select length( abcdef ) from dual
8,initcap(首字母变大写) ,lower(变小写),upper(变大写)
0select lower( ABC ) s1,
upper( def ) s2,
initcap( efg ) s3 from dual.
9,Replace
0select replace( abc , b , xy ) from dual.
10,translate
0select translate( abc , b , xx ) from dual. -- x是1位
11,lpad [左添充] rpad [右填充](用于控制输出格式)
0select lpad( func ,15, = ) s1, rpad( func ,15, - ) s2 from dual.
0select lpad(dname,14, = ) from dept.
12, decode[实现if ..then 逻辑]
0select deptno,decode(deptno,10, 1 ,20, 2 ,30, 3 , 其他 ) from dept.
三)数字函数
1,取整函数(ceil 向上取整,floor 向下取整)
0select ceil(66.6) N1,floor(66.6) N2 from dual.
2, 取幂(power) 和 求平方根(sqrt)
0select power(3,2) N1,sqrt(9) N2 from dual.
3,求余
0select mod(9,5) from dual.
4,返回固定小数位数 (round:四舍五入,trunc:直接截断)
0select round(66.667,2) N1,trunc(66.667,2) N2 from dual.
5,返回值的符号(正数返回为1,负数为-1)
0select sign(-32),sign(293) from dual.
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