一些常用查询SQL语句以及显示格式

1.查询当前年、月、周相关时间

1.1.查询当前年份

SELECT TO_CHAR(SYSDATE,"YYYY") AS YEAR FROM DUAL--查询当前年份
SELECT TO_CHAR(SYSDATE,"YYY") AS YEAR FROM DUAL--查询当前年份后两位
SELECT TO_CHAR(SYSDATE,"YY") AS YEAR FROM DUAL--查询当前年份最后两位
SELECT TO_CHAR(SYSDATE,"Y") AS YEAR FROM DUAL--查询当前年份最后一位

1.2.查询当前年份第几天

SELECT TO_CHAR(SYSDATE,"DDD") AS DAYS FROM DUAL

1.3.查询当前月份第几天

SELECT TO_CHAR(SYSDATE,"DD") AS DAYS FROM DUAL

1.4.查询当前周的星期几

SELECT TO_CHAR(SYSDATE,"dy") AS WEEK FROM DUAL
SELECT TO_CHAR(SYSDATE,"day") AS WEEK FROM DUAL 

1.5.查询当前年的第几天：

SELECT TO_CHAR(SYSDATE,"DDD") AS DAYS FROM DUAL

2.查询当前第几季度

SELECT TO_CHAR(SYSDATE,"Q") AS JD FROM DUAL

3.查询当前在一年内是第几周

SELECT TO_CHAR(SYSDATE,"IW") AS WEEKNUM FROM DUAL
SELECT TO_CHAR(SYSDATE,"WW") AS WEEKNUM FROM DUAL
SELECT TO_CHAR(SYSDATE,"W") AS WEEKNUM FROM DUAL

4.查询当前某年某月有多少天

SELECT TO_CHAR(last_day(to_date("2019/02/01","YYYY/MM/DD")),"DD") AS MONTH_DAYS_NUMBER FROM DUAL

5.查询当前的日期格式

SELECT TO_CHAR(SYSDATE,"YYYY/MM/DD") AS MONTH FROM DUAL--获取当前日期的"YYYY/MM/DD"格式：2020/01/02
SELECT TO_CHAR(SYSDATE,"YYYYMMDD") AS MONTH FROM DUAL--获取当前日期的"YYYYMMDD"格式：20200102
SELECT TO_CHAR(SYSDATE,"YYYYMMDD HH:MI:SS") AS now FROM DUAL--获取当前时间，精确到秒的12小时制格式：20200102 03:18:25
SELECT TO_CHAR(SYSDATE,"YYYYMMDD HH24:MI:SS") AS now FROM DUAL--获取当前时间，精确到秒24小时制的格式：20200102 15:18:13
SELECT TO_CHAR(SYSDATE,"YYYY/MM/DD HH24:MI:SS:PM:DY") AS now FROM DUAL--获取当前时间的格式，显示上、下午和星期几：2020/01/02 15:17:59:下午：星期四

6.查询距离当前时间一段时间间隔的时间，当前时间之前用“-”当前时间之后用“+”

SELECT TO_CHAR(SYSDATE, "YYYY/MM/DD HH24:MI:SS") AS NOW,TO_CHAR(SYSDATE - INTERVAL "7" second,"YYYY/MM/DD HH24:MI:SS") AS PAST FROM DUAL --查询当前时间的7秒前时间
SELECT TO_CHAR(SYSDATE, "YYYY/MM/DD HH24:MI:SS") AS NOW,TO_CHAR(SYSDATE - INTERVAL "7" minute,"YYYY/MM/DD HH24:MI:SS") AS PAST FROM DUAL --查询当前时间的7分钟前时间
SELECT TO_CHAR(SYSDATE, "YYYY/MM/DD HH24:MI:SS") AS NOW,TO_CHAR(SYSDATE - INTERVAL "7"hour ,"YYYY/MM/DD HH24:MI:SS") AS PAST FROM DUAL --查询当前时间的7小时前时间
SELECT TO_CHAR(SYSDATE, "YYYY/MM/DD HH24:MI:SS") AS NOW,TO_CHAR(SYSDATE - INTERVAL "7"day ,"YYYY/MM/DD HH24:MI:SS") AS PAST FROM DUAL --查询当前时间的7天前时间
SELECT TO_CHAR(SYSDATE, "YYYY/MM/DD HH24:MI:SS") AS NOW,TO_CHAR(SYSDATE - INTERVAL "7"month ,"YYYY/MM/DD HH24:MI:SS") AS PAST FROM DUAL --查询当前时间的7月前时间
SELECT TO_CHAR(SYSDATE, "YYYY/MM/DD HH24:MI:SS") AS NOW,TO_CHAR(SYSDATE - INTERVAL "7"year ,"YYYY/MM/DD HH24:MI:SS") AS PAST FROM DUAL --查询当前时间的7年前时间
SELECT TO_CHAR(SYSDATE, "YYYY/MM/DD HH24:MI:SS") AS NOW,TO_CHAR(SYSDATE - 8*INTERVAL "7"hour ,"YYYY/MM/DD HH24:MI:SS") AS PAST FROM DUAL --查询当前时间参数年、月、日、时、分、秒乘以一个数字倍数之前的时间