1.字符串转日期：
to_date(paramStr,'YYYYMMDDHH24MISS')
to_date(paramStr,'yyyy-MM-DD')
to_date(paramStr,'yyyy/mm/dd hh24:mi:ss')
to_date(paramStr,'yyyy-MM-dd hh24:mi:ss')
2.日期转字符串
to_char(paramDate,'HH24:MI:SS')
to_char(paramDate,'yyyy-MM-DD HH24:MI:SS')
to_char(paramDate,'YYYY-MM-DD')
to_char(paramDate,'YYYYMMDD')
3.字符串函数
nvl(paramStr,specStr)--其中参数specStr 为指定要转成的具体字符或数字
4.字符串截取函数
substr(paramStr,beginIndex,len)--从指定索引位置beginIndex（不支持下标从0开始，不可缺省），截取指定长度len的字符串
5.左侧补充特定字符串函数
lpad(paramStr, padded_length, [ pad_string ])
6.支持字符串连接关键字 || （不允许使用+进行字符串连接）
7.select @allFeee=(select sum(CONVERT(numeric(19,4),price)) from (select price from queuedetail t where t.appointsid =@p_APPOINTSID) temp)
日期函数
SELECT ROUND(DATE'2005-5-10', 'MONTH'),
ROUND(DATE'2005-6-16', 'MONTH')
FROM dual;
SELECT NEXT_DAY(SYSDATE,'星期二') FROM dual;
SELECT TRUNC(SYSDATE, 'YEAR') FROM dual;
SELECT TRUNC(SYSDATE,'DAY') FROM dual;
SELECT TRUNC(SYSDATE) FROM dual;
SELECT EXTRACT(YEAR FROM SYSDATE) FROM dual;
字符函数
select initcap('hello') from dual;
select lower('FUN') from dual;
select upper('sun') from dual;
select ltrim( 'xyzadams','xyz') from dual;
select rtrim('xyzadams','ams') from dual;
select translate('jack','abcd' ,'1234') from dual;
select replace('jack and jue' ,'j','bl') from dual;
select instr ('worldwide','d') from dual;
select substr('abcdefg',3,2) from dual;
select concat ('Hello',' world') from dual;
SELECT CHR(67) FROM dual;
SELECT LPAD('function',15,'=') FROM dual;
SELECT TRIM (LEADING 9 FROM 99998769789999) FROM dual;
SELECT TRIM (TRAILING 9 FROM 99998769789999) FROM dual;
SELECT TRIM (9 FROM 9999876789999) FROM dual;
SELECT LENGTH('frances') FROM dual;
SELECT orderno, DECODE(ostatus,'p','准备处理','c','已完成')
FROM order_master;
数字函数
select abs(-15) from dual;
select ceil(44.778) from dual;
select sin(1.571) from dual;
select cos(0) from dual;
select sign(-32) from dual;
select floor(100.2) from dual;
select power(4,2) from dual;
select mod(10,3) from dual;
select round(100.256,2) from dual;
select trunc(100.256,2) from dual;
select sqrt(4) from dual;
SELECT TO_CHAR(sysdate,'YYYY"年"fmMM"月"fmDD"日" HH24:MI:SS') FROM dual;
SELECT TO_CHAR(itemrate,'C99999') FROM itemfile;
SELECT TO_DATE('2005-12-06' , 'yyyy-mm-dd') FROM dual;
SELECT SQRT(TO_NUMBER('100')) FROM dual;
SELECT itemdesc, NVL(re_level,0) FROM itemfile;
SELECT itemdesc,NVL2(re_level,re_level,max_level)
FROM itemfile;
SELECT itemdesc,NULLIF(re_level,max_level)
FROM itemfile;
分组函数
SELECT AVG (re_level) FROM itemfile
WHERE p_category='accessories';
SELECT MIN(max_level) FROM itemfile
WHERE p_category='spares';
SELECT SUM(itemrate*max_level) FROM itemfile;
SELECT * FROM itemfile;
SELECT COUNT(*) FROM itemfile;
SELECT COUNT(itemrate) FROM itemfile;
SELECT COUNT(DISTINCT p_category) FROM itemfile;
SELECT p_category,MAX(itemrate) FROM itemfile
GROUP BY p_category;
SELECT p_category,MAX(itemrate) FROM itemfile
GROUP BY p_category
HAVING p_category NOT IN ('accessories');
分析函数
SELECT ename, job, deptno, sal, ROW_NUMBER() OVER
(ORDER BY sal DESC) AS SAL_RANK
FROM SCOTT.EMP;
SELECT ename, job, deptno, sal, ROW_NUMBER() OVER
(PARTITION BY deptno ORDER BY sal DESC) AS SAL_RANK
FROM SCOTT.EMP;
SELECT ename, sal, comm, deptno,
RANK() OVER (PARTITION BY deptno
ORDER BY sal DESC, comm) RANK
FROM scott.emp;
SELECT d.dname, e.ename, e.sal, DENSE_RANK()
OVER (PARTITION BY e.deptno ORDER BY e.sal DESC) DENSERANK
FROM emp e, dept d
WHERE e.deptno = d.deptno;