Oracle:

1. 截取字符串中字符前的字符串(不包括字符)

select  Substr(P.SCHEDULE_CODE, 1, Instr(P.SCHEDULE_CODE, '(', 1)-1)  from M_SUB_TASK_SCHEDULE_LOG P;

2. 截取字符串中字符前的字符串(包括字符)

select Substr(P.SCHEDULE_CODE, 1, Instr(P.SCHEDULE_CODE, '(ret', 1))  from M_SUB_TASK_SCHEDULE_LOG P;

3.两个date格式的日期相减得时分秒

SELECT

EXTRACT(DAY FROM (sysdate-to_date('2012-03-29 00:00:00','YYYY-MM-DD HH24:MI:ss')) DAY TO SECOND )

|| ' days '

|| EXTRACT(HOUR FROM (sysdate-to_date('2012-03-29 00:00:00','YYYY-MM-DD HH24:MI:ss')) DAY TO SECOND )

|| ' hours'

|| EXTRACT(MINUTE FROM (sysdate-to_date('2012-03-29 00:00:00','YYYY-MM-DD HH24:MI:ss')) DAY TO SECOND )

|| ' minute'

|| EXTRACT(SECOND FROM (sysdate-to_date('2012-03-29 00:00:00','YYYY-MM-DD HH24:MI:ss')) DAY TO SECOND )

|| ' second' "Interval"

FROM DUAL;

或

SELECT (--TO_NUMBER(SUBSTR(D21, 1, INSTR(D21, ' '))) ||

SUBSTR(D21, INSTR(D21, ' ') + 1, 2) ||

SUBSTR(D21, INSTR(D21, ' ') + 4, 2)||

SUBSTR(D21, INSTR(D21, ' ') + 7, 2))TIME1,

t.BEGIN_TIMESTAMP,

t.END_TIMESTAMP

FROM (SELECT CAST(P.END_TIMESTAMP AS TIMESTAMP) - CAST(P.BEGIN_TIMESTAMP AS TIMESTAMP) D21,

BEGIN_TIMESTAMP,END_TIMESTAMP FROM M_SUB_TASK_SCHEDULE_LOG P)t ;

MySql:

1.截取第一个 '(' 之前的所有字符(顺数)

SELECT SUBSTRING_INDEX(P.SCHEDULE_CODE, '(', 1) FROM M_SUB_TASK_SCHEDULE_LOG P;

2.截取第一个 '(' 之前的所有字符(倒数)

SELECT SUBSTRING_INDEX(P.SCHEDULE_CODE, '(', -1) FROM M_SUB_TASK_SCHEDULE_LOG P;