标签：mes expr cond ascii use 返回 rom oracl turn
一、单行函数
1.定义：对表或视图的查询时，针对每行记录返回一个值的函数。
2.用途：用于select语句，where条件
3.分类：
数值函数 Number Functions
字符函数(返回字符) Character Functions Returning Character Values
字符函数(返回数值) Character Functions Returning Number Values
日期函数 Datetime Functions
转换函数 Conversion Functions
其它单值函数 Miscellaneous Single-Row Functions
二、数值函数
数值函数：接收一个数值参数，返回一个数值结果的函数。
常用函数：
1.MOD(m,n) m/n取余函数
SELECT MOD(11,4) "Modulus" FROM DUAL;
2.ABS(n) 取绝对值函数
SELECT ABS(-15) "Absolute" FROM DUAL;
3.SIGN(n) 符号函数，正数返回1，负数返回-1，0返回0
SELECT SIGN(-15) "Sign" FROM DUAL;
4.CEIL(n) 向上取整函数
SELECT CEIL(15.7) "Ceiling" FROM DUAL;
5.FLOOR(n) 向下取整函数
SELECT FLOOR(15.7) "Floor" FROM DUAL;
6.ROUND(m)/ROUND(m,n) 四舍五入函数
SELECT ROUND(15.193) "Round" FROM DUAL;
SELECT ROUND(15.193,1) "Round" FROM DUAL;
SELECT ROUND(15.193,-1) "Round" FROM DUAL;
7.TRUNC(m)/TRUNC(m,n) 截断函数
SELECT TRUNC(15.79) "Truncate" FROM DUAL;
SELECT TRUNC(15.79,1) "Truncate" FROM DUAL;
SELECT TRUNC(15.79,-1) "Truncate" FROM DUAL;
不常用函数：
1.POWER(m,n) m的n次方函数
SELECT POWER(10,2) "Raised" FROM DUAL;
2.SQRT 平方根函数
SELECT SQRT(25) "Square root" FROM DUAL;
3.LOG(m,n) n的m次方根函数
SELECT LOG(10,100) "Log base 10 of 100" FROM DUAL;
SELECT LOG(10,POWER(10,2)) "Log base 10 of 100" FROM DUAL;
4.EXP e(e = 2.71828183)的m次方函数
SELECT EXP(4) "e to the 4th power" FROM DUAL;
5.LN m的e(e = 2.71828183)次方根函数
SELECT LN(exp(4)) "Natural log of exp(4)" FROM DUAL;
6.SIN 正玄函数
SELECT SIN(30 * 3.14159265359/180) "Sine of 30 degrees" FROM DUAL;
7.COS 余玄函数
SELECT COS(60 * 3.14159265359/180) "Cosine of 60 degrees" FROM DUAL;
8.TAN 正切函数
SELECT TAN(45 * 3.14159265359/180) "Tangent of 45 degrees" FROM DUAL;
9.ASIN 反正玄函数
SELECT ASIN(0.5) "Arc_Sine" FROM DUAL;
SELECT ASIN(SIN(30 * 3.14159265359/180)) "Arc_Sine" FROM DUAL;
10.ACOS 反余玄函数
SELECT ACOS(COS(60 * 3.14159265359/180)) "Arc_Cosine" FROM DUAL;
11.ATAN 反正切函数
SELECT ATAN(TAN(45 * 3.14159265359/180)) "Arc_Tangent" FROM DUAL;
12.ATAN2
SELECT ATAN2(0.3, 0.2) "Arc_Tangent2" FROM DUAL;
13.SINH 双曲正玄
SELECT SINH(1) "Hyperbolic sine of 1" FROM DUAL;
14.COSH 双曲余玄函数
SELECT COSH(0) "Hyperbolic cosine of 0" FROM DUAL;
15.TANH 双曲正切
SELECT TANH(.5) "Hyperbolic tangent of .5" FROM DUAL;
三、字符函数(返回字符) Character Functions Returning Character Values
1.CHR(n) 将数字转换为ASCII码
select CHR(65) from dual;
2.CONCAT(m,n) 连接字符串,等同于连接操作符||
select CONCAT(‘A‘,‘B‘) from dual;
select CONCAT(CONCAT(‘A‘,‘B‘),‘C‘) from dual;
select ‘A‘||‘B‘||‘C‘ from dual;
3.INITCAP(n) 将字符中单词的首字母大写
SELECT INITCAP(‘hello sql‘) "Capitals" FROM DUAL;
4.UPPER(n) 将字符中字母大写
SELECT UPPER(‘hello sql‘) "Uppercase" FROM DUAL;
5.LOWER(n) 将字符中字母小写
SELECT LOWER(‘HELLO SQL‘) "Lowercase" FROM DUAL;
6.LPAD(c1,n,c2) 从左侧补齐字符串的长度
SELECT LPAD(‘Page 1‘,15,‘*.‘) "LPAD example" FROM DUAL;
SELECT LPAD(‘Page 1‘,15) "LPAD example" FROM DUAL;
7.RPAD(c1,n,c2) 从右侧补齐字符串的长度
SELECT RPAD(‘Page 1‘,15,‘*.‘) "LPAD example" FROM DUAL;
SELECT RPAD(‘Page 1‘,15) "LPAD example" FROM DUAL;
8.TRIM 修剪前后两端的空格或指定字符
SELECT TRIM (‘ AB C ‘) "TRIM Example" from dual;
--SELECT TRIM (‘00098702348900‘,‘0‘) "TRIM Example" from dual;
SELECT TRIM (0 FROM 00098702348900) "TRIM Example" from dual;
9.LTRIM 修剪前端的空格或指定字符
SELECT LTRIM (‘ AB C ‘) "LTRIM Example" from dual;
SELECT LTRIM (‘00098702348900‘,‘0‘) "LTRIM Example" from dual;
10.RTRIM 修剪后端的空格或指定字符
SELECT RTRIM (‘ AB C ‘) "RTRIM Example" from dual;
SELECT RTRIM (‘00098702348900‘,‘0‘) "RTRIM Example" from dual;
11.SUBSTR(c,p,l) 从字符串指定位置截取指定长度的子字符串
SELECT SUBSTR(‘ABCDEFG‘,3,4) "Substring" FROM DUAL;
SELECT SUBSTR(‘ABCDEFG‘,3) "Substring" FROM DUAL;
SELECT SUBSTR(‘ABCDEFG‘,-3) "Substring" FROM DUAL;
SELECT SUBSTR(‘ABCDEFG‘,-3,4) "Substring" FROM DUAL;
SELECT SUBSTR(‘ABCDEFG‘,1,2) "Substring" FROM DUAL;
SELECT SUBSTR(‘ABCDEFG‘,0,2) "Substring" FROM DUAL;
SELECT SUBSTR(‘我是老师‘,1,4) "Substring" FROM DUAL;
SELECT SUBSTRB(‘我是老师‘,1,4) "Substring" FROM DUAL;
SELECT SUBSTRB(‘我是老师‘,1,3) "Substring" FROM DUAL;
SELECT SUBSTRB(‘A我B是C老F师G‘,1,3) "Substring" FROM DUAL;
SELECT SUBSTRC(‘我是老师‘,1,3) "Substring" FROM DUAL;
SELECT SUBSTR(‘A我B是C老F师G‘,1,3) "Substring" FROM DUAL;
SELECT SUBSTRC(‘A我B是C老F师G‘,1,3) "Substring" FROM DUAL;
12.REPLACE(c,sc,rc) 从c字符串中找到sc子串并用rc子串进行替换
SELECT REPLACE(‘JACK and JUE‘,‘J‘,‘BL‘) "Changes" FROM DUAL;
SELECT REPLACE(‘我是老师‘,‘‘,‘*‘) FROM DUAL;
SELECT REPLACE(‘我是老师‘,‘‘) FROM DUAL;
13.TRANSLATE(c,from_c,to_c) 格式转化，按照from_c到to_c的模式转化字符串c
SELECT TRANSLATE(‘2KRW229‘,‘0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ‘,
‘9999999999XXXXXXXXXXXXXXXXXXXXXXXXXX‘) "License" FROM DUAL;
SELECT TRANSLATE(‘2KRW229‘,‘0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ‘,
‘0123456789‘) FROM DUAL;
select TRANSLATE(‘2018‘,‘0123456789‘,‘零一二三四五六七八九‘) from dual;
select TRANSLATE(‘1588‘,‘0123456789‘,‘零壹贰叁肆伍陆柒捌玖‘) from dual;
四、字符函数(返回数值) Character Functions Returning Number Values
1.ASCII(c) 返回字符的ASCII码
SELECT ASCII(‘A‘) FROM DUAL;
2.INSTR(string,substring,position,occurrence)
查找，返回子字符串的位置
SELECT INSTR(‘CORPORATE FLOOR‘,‘O‘) "Instring" FROM DUAL;
SELECT INSTR(‘CORPORATE FLOOR‘,‘OR‘) "Instring" FROM DUAL;
SELECT INSTR(‘CORPORATE FLOOR‘,‘OR‘,3) "Instring" FROM DUAL;
SELECT INSTR(‘CORPORATE FLOOR‘,‘OR‘,-3) "Instring" FROM DUAL; --位置参数是负数时，从右向左找。
SELECT INSTR(‘CORPORATE FLOOR‘,‘OR‘,3,2) "Instring" FROM DUAL;
SELECT INSTR(‘CORPORATE FLOOR‘,‘OR‘,-3,2) "Instring" FROM DUAL;
select ename,INSTR(ename,‘O‘) ,substr(ename,INSTR(ename,‘O‘)) from emp
3.LENGTH(c) 返回字符串长度
SELECT LENGTH(‘ABCDEFG‘) "Length in characters" FROM DUAL;
SELECT LENGTH(‘我是老师‘) "Length in characters" FROM DUAL;
SELECT LENGTHB(‘ABCDEFG‘) "Length in bytes" FROM DUAL;
SELECT LENGTHB(‘我是老师‘) "Length in bytes" FROM DUAL;
五、日期函数 Datetime Functions
日期 +/- 数字 = 日期
SELECT sysdate+5,sysdate-10 FROM DUAL;
日期 - 日期 = 数字
SELECT sysdate-TO_DATE(‘2017-08-16‘,‘yyyy-mm-dd‘) FROM DUAL;
1.SYSDATE 当前日期 SYSTIMESTAMP、CURRENT_DATE、
CURRENT_TIMESTAMP、LOCALTIMESTAMP
select sysdate from dual;
select sysdate,SYSTIMESTAMP,CURRENT_DATE,
CURRENT_TIMESTAMP,LOCALTIMESTAMP from dual;
2.LAST_DAY(date) 取本月最后1天
select sysdate,last_day(sysdate) from dual;
3.NEXT_DAY(date,n) 获取下个星期几的日期
select sysdate,next_day(sysdate,1) from dual;
4.ADD_MONTHS(d,n) 月份加减数字
select sysdate,add_months(sysdate,1),add_months(sysdate,-2),
add_months(sysdate,0.5) from dual;
5.MONTHS_BETWEEN(d1,d2) 月份相减
SELECT MONTHS_BETWEEN(sysdate,TO_DATE(‘2017-08-16‘,‘yyyy-mm-dd‘)) "Months" FROM DUAL;
6.EXTRACT (类型 from date) 从日期中提取年月日时分秒
SELECT EXTRACT(YEAR FROM DATE ‘2017-03-07‘) FROM DUAL;
SELECT EXTRACT(MONTH FROM sysdate) FROM DUAL;
SELECT EXTRACT(DAY FROM sysdate) FROM DUAL;
SELECT EXTRACT(HOUR FROM LOCALTIMESTAMP) FROM DUAL;
SELECT EXTRACT(MINUTE FROM LOCALTIMESTAMP) FROM DUAL;
SELECT EXTRACT(SECOND FROM LOCALTIMESTAMP) FROM DUAL;
7.TRUNC(date) 日期截断
SELECT TRUNC(sysdate, ‘yyyy‘) "New Year" FROM DUAL;
SELECT TRUNC(sysdate, ‘mm‘) "New Months" FROM DUAL;
SELECT TRUNC(sysdate, ‘dd‘) "New Day" FROM DUAL;
SELECT TRUNC(sysdate, ‘hh24‘) "New Hour" FROM DUAL;
SELECT TRUNC(sysdate, ‘mi‘) "New Minute" FROM DUAL;
8.ROUND(date) 日期四舍五入
SELECT ROUND(sysdate, ‘yyyy‘) "New Year" FROM DUAL;
SELECT ROUND(sysdate, ‘mm‘) "New Year" FROM DUAL;
SELECT ROUND(sysdate, ‘dd‘) "New Year" FROM DUAL;
SELECT ROUND(sysdate, ‘hh24‘) "New Year" FROM DUAL;
SELECT ROUND(sysdate, ‘mi‘) "New Year" FROM DUAL;
六、转换函数 Conversion Functions
转换函数：将数值从一个类型转换到另一个类型。
1.BIN_TO_NUM 二进制转数字
SELECT BIN_TO_NUM(1,0,1,0) FROM DUAL;
2.TO_CHAR (datetime) 日期转字符串
SELECT to_char(sysdate,‘yyyy-mm-dd hh24:mi:ss‘) from dual;
3.TO_DATE 字符串转日期
SELECT sysdate - to_date(‘2017-01-01‘,‘yyyy-mm-dd‘) from dual;
4.TO_NUMBER 字符转数字
SELECT to_number(‘012345‘) from dual;
SELECT to_number(‘0123.45‘,‘9999D99‘) from dual;
SELECT to_number(‘$0123.45‘,‘$9999D99‘) from dual;
七、其它单值函数 Miscellaneous Single-Row Functions
1.DECODE 条件选择函数
SELECT emp.*,decode(deptno,10,‘ACCOUNTING‘,
20,‘RESEARCH‘,30,‘SALES‘,‘OPERATIONS‘) from emp;
SELECT emp.*,decode(sign(sal-1600),
1,‘工资大于1600‘,0,‘工资等于1600‘,-1,‘工资小于1600‘) from emp;
SELECT emp.*,decode(sign(instr(ename,‘A‘)),
1,‘名字包含A‘,0,‘名字不包含A‘) from emp;
2.coalesce (expr1, expr2, ..., exprn) 返回首个非空表达式
SELECT emp.*,COALESCE (comm,0) from emp;
3.NVL(c,v) NVL2(c,v1,v2) 空值转化
SELECT emp.*,sal+comm,sal+nvl(comm,0) from emp;
SELECT emp.*,nvl2(comm,sal+comm,sal) from emp;
4.USER 返回当前用户名\ID
SELECT USER from dual;
SELECT UID FROM DUAL;
5.SYS_GUID 返回由16字节组成的全局唯一标识符（原始值）。
SELECT SYS_GUID() from dual;
6.NULLIF(s1,s2) s1与s2相等时返回空，不等时返回s1
SELECT emp.deptno,dept.deptno,
nullif(emp.deptno,dept.deptno) from emp,dept;
7.GREATEST 返回集合中最大值
SELECT GREATEST (‘A‘, ‘B‘, ‘C‘) "Greatest" FROM DUAL;
8.LEAST 返回集合中最小值
SELECT LEAST (‘A‘, ‘B‘, ‘C‘) "least" FROM DUAL;
标签：mes expr cond ascii use 返回 rom oracl turn
原文地址：https://www.cnblogs.com/BradMiller/p/9279548.html
