—-
SQL> select greatest(111,222) from dual;
GREATEST(111,222)
—————–
222
SQL> select least(111,222) from dual;
LEAST(111,222)
————–
111
SQL> select floor(-7.8) from dual;
select sys_guid() from dual;
SYS_GUID()
——————————–
52E859DC8A9D0DA8E053FB6410AC9549
insert into t1 values(‘我们’);
insert into t1 values(‘我你’);
insert into t1 values(‘你们’);
insert into t1 values(‘吃饭’);
insert into t1 values(‘他’);
> select * from t1 order by nlssort(name,’nls_sort=schinese_pinyin_m’);
SQL> select systimestamp from dual;
SQL> select vsize(ename) “byte” from emp where deptno=30;
SQL> select ora_hash(ename) from emp;
SQL> select extract( hour from sysdate) year from emp;
SQL> select sign(3434) from dual;
——————————————
regular expression
regexp_count
regexp_instr
regexp_replace
regexp_substr
regexp_like
regexp_like
SQL> select ename from emp where regexp_like(ename,’A|S’);
SQL> select ename from emp where ename like ‘%A%’ or ename like ‘%S%’;
SQL> select ename from emp where regexp_like(ename,’^A’);
SQL> select ename from emp where regexp_like(ename,’G$’);
SQL> select ename from emp where regexp_like(ename,’^[A-z]+$’);
SQL> select ename from emp where regexp_like(ename,’s’,’c’);
no rows selected
SQL> select ename from emp where regexp_like(ename,’S’,’i’);
regexp_replace
selelect replace(‘abc’,’a’,’d’)
select regexp_replace(‘abcabc’,’a’,’0′,1,2,’i’) from dual;
regexp_instr
SELECT REGEXP_INSTR(‘1234567890’, ‘(123)(4(56)(78)0)’, 1, 1, 1, ‘i’,1)
“REGEXP_INSTR” FROM DUAL;
0123(((abc)(de)f)ghi)45(678)
abcdefghi abcdef abc de 678
((河北省)(邢台)(沙河))
河北省邢台啊啊
河北省邢台版本
河北生石家庄
regexp_substr
select susbtr(‘172.16.50.1’,)
172.16.100.1
172.168.9.
172.16.100.2
SELECT
REGEXP_SUBSTR(‘500 Oracle Parkway, Redwood Shores, CA’,
‘,[^,]+,’) “REGEXPR_SUBSTR”
FROM DUAL;
^[,]
[^,]
SELECT REGEXP_COUNT(‘123123123123’, ‘123’, 3, ‘i’) COUNT FROM DUAL;
DECODE
CASE
10 +1000
20 +1500
30 x
40 -500
sign
sal
<2000
2000-4350 1%
4350+ 2%
select
decode sal,sal<2000,sal,
sal>=2000 and sal<4000, sal*0.99
case
select
case when sal<2000 then sal
when between 2000 and 4000 then sal*0.99
else sal*0.98
end sal
from
emp;
select
case when deptno =10 then sal+1000
when deptno=20 then sal+2000
else sal
end sal,
case deptno when 10 then sal+1000
when 20 then sal+2000
else sal
end sal,
from
emp;
————————————————
最大值 最小值 平均值 求和 统计
max min avg sum count()
字符
数字
日期
—————————————————
分组函数
select … group by
(1) 聚集函数
(2) 加到group by后面
select
name,
sum(case subject when ‘语文’ then grade else 0 end) “语文”,
max(case when subject=’英语’ then grade else 0 end ) “英语”,
sum(decode(subject,’数学’,grade,0)) “数学”
from
t4
group by name;
select ‘我们’ from dual;
