[Oracle] 获取系统当前日期

获取Oracle系统当前日期，我们可以考虑使用SYSDATE的参数

SELECT SYSDATE AS sdate,                                 -- 系统完整日期时间TO_CHAR(SYSDATE, 'YYYY')  AS "sdate_year4",       -- 年(4位)TO_CHAR(SYSDATE, 'YY')    AS "sdate_year2",       -- 年(2位)TO_CHAR(SYSDATE, 'MM')    AS "sdate_month2",      -- 月(数字)TO_CHAR(SYSDATE, 'MON')   AS "sdate_mon",         -- 月(数字+月)TO_CHAR(SYSDATE, 'DD')    AS "sdate_day",         -- 日TO_CHAR(SYSDATE, 'IW')    AS "sdate_week",        -- 周数TO_CHAR(SYSDATE, 'Q')     AS "sdate_quarter",     -- 季度(1-4)-- 季节CASE WHEN TO_CHAR(SYSDATE, 'MM') IN ('12','01','02') THEN '冬季'WHEN TO_CHAR(SYSDATE, 'MM') IN ('03','04','05') THEN '春季'WHEN TO_CHAR(SYSDATE, 'MM') IN ('06','07','08') THEN '夏季'ELSE '秋季'END AS "sdate_season",TO_CHAR(SYSDATE, 'AM')    AS "sdate_ampm",        -- AM/PMTO_CHAR(SYSDATE, 'HH24')  AS "sdate_hour24",      -- 小时(24小时制)TO_CHAR(SYSDATE, 'MI')    AS "sdate_minute",      -- 分钟TO_CHAR(SYSDATE, 'SS')    AS "sdate_second",      -- 秒钟TO_CHAR(ADD_MONTHS(TRUNC(SYSDATE, 'MM'), 1) - 1, 'DD') AS "sdate_month_days",  -- 当月天数TO_CHAR(LAST_DAY(SYSDATE), 'MM-DD') AS "sdate_last_day_of_month",              -- 当月最后一天-- YYYY-MM-DD HH:MI:SSTO_CHAR(SYSDATE, 'YYYY-MM-DD HH24:MI:SS')AS "sdate_iso_format",                -- YYYY年MM月DD日TO_CHAR(SYSDATE, 'YYYY"年"MM"月"DD"日"') AS "sdate_chinese_format"             
FROM DUAL;

日期时间也可进行加减乘除的运算

-- 当前时间减去6分钟的时间
SELECT sysdate, sysdate - interval '6' minute AS res1 FROM dual;
-- 当前时间减去6小时的时间
SELECT sysdate, sysdate - interval '6' hour AS res2 FROM dual;
-- 当前时间减去6天的时间
SELECT sysdate, sysdate - interval '6' day AS res3 FROM dual;
-- 当前时间减去6月的时间
SELECT sysdate, sysdate - interval '6' month AS res4 FROM dual;
-- 当前时间减去6年的时间
SELECT sysdate, sysdate - interval '6' year AS res5 FROM dual;
-- 时间间隔乘以一个数字
SELECT sysdate, sysdate - 8*interval '6' hour AS res6 FROM dual;

输出结果：

补充扩展：Oracle获取当月所有日期

SELECT TRUNC(SYSDATE, 'MM') + ROWNUM - 1 FROM DUAL CONNECT BY ROWNUM <= TO_NUMBER(TO_CHAR(LAST_DAY(SYSDATE), 'dd'));