oracle常用函数案例

--INSTR函数
SELECT INSTR(' HELLO WORLD','H') FROM DUAL;
--LTRIM RTRIM函数
SELECT LTRIM('*HELLO=','*') FROM DUAL;
SELECT RTRIM('=HELLO=','=') FROM DUAL;
SELECT RTRIM(LTRIM('*HELLO*','*'),'*') FROM DUAL;
--TRIM函数
SELECT TRIM('*'FROM'*HELLO*') FROM DUAL;
--REPLACE函数
SELECT REPLACE('ABCDE','E','123') FROM DUAL;
--SUBSTR函数
SELECT SUBSTR('ABCDE',2,2) FROM DUAL;
--CEIL FLOOR函数
SELECT CEIL(6.01) FROM DUAL;
SELECT FLOOR(6.999) FROM DUAL;
--ROUND函数
SELECT ROUND(3.456,1) FROM DUAL;
--TRUNC函数            
SELECT TRUNC(3.456,1) FROM DUAL;
--RXTRACT函数
SELECT 
SYSDATE "DATE",
EXTRACT(YEAR FROM SYSDATE) "YEAR",
EXTRACT(MONTH FROM SYSDATE) "MONTH",
EXTRACT(DAY FROM SYSDATE) "DAY",
EXTRACT(HOUR FROM SYSTIMESTAMP) "HOUR",--HOUR匹配的结果没有加上时区，在中国运行的结果要小8个小时
EXTRACT(MINUTE FROM SYSTIMESTAMP) "MINUTE",
EXTRACT(SECOND FROM SYSTIMESTAMP) "SECOND"
FROM DUAL;
--TO_CHAR函数
SELECT
TO_CHAR(SYSDATE,'YYYY"年"MM"月"DD"日" HH24:MI:SS') "DATE" 
FROM DUAL