SQL common date query statement and display format setting

1. Query the relevant time of the current year, month and week

1.1. Query the current year

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. Query the day of the current year

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

1.3. Query the day of the current month

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

1.4. Query the day of the week in the current week

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

1.5. Query the day of the current year:

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

2. Query the current quarter

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

3. Query the current week in a year

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. Query the number of days in a certain month in the current year

SELECT TO_CHAR(last_day(to_date('2023/06/03','YYYY/MM/DD')),'DD') AS MONTH_DAYS_NUMBER FROM DUAL

5. Query the current date format

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. Query the time interval from the current time, use "-" before the current time and use "+" after the current time

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

Date and time functions in SqlServer

function	parameter/function
getDate()	Returns the current date and time of the system
DateDiff (interval,date1,date2)	In the way specified by interval, return the difference between date2 and date1 date2-date1
DateAdd (interval,number,date)	In the way specified by interval, add the date after number
DatePart (interval,date)	Returns the integer value corresponding to the part specified by interval in date
DateName (interval,date)	Returns the string name corresponding to the part specified by interval in date

The setting value of the parameter interval is as follows:

value	Abbreviation (Sql Server)	Access and ASP	illustrate
Year	Yy	yyyy	Year 1753 ~ 9999
Quarter	Qq	q	Season 1 ~ 4
Month	Mm	m	month 1 ~ 12
Day of year	Dy	y	The number of days in a year, the day of the year 1-366
Day	Dd	d	Sun, 1-31
Weekday	Dw	w	The number of days of the week, the number of days of the week 1-7
Week	Wk	ww	Week, the week of the year 0 ~ 51
Hour	Hh	h	hour 0 ~ 23
Minute	Mi	n	minutes 0 ~ 59
Second	Ss	s	seconds 0 ~ 59
Millisecond	Ms	-	milliseconds 0 ~ 999

The method of querying the first 10 items in SQL is as follows:

select top X *  from table_name    
select top X *  from table_name order by colum_name desc
--MySQL、Sqlite查询前10条数据的方法：
select * from table_name limit 0,10  
--ORACLE查询前10条的方法：
select * from table_name where rownum<X

SQL common (query date) statement

SQL common date query statement and display format setting

1. Query the relevant time of the current year, month and week

2. Query the current quarter

3. Query the current week in a year

Date and time functions in SqlServer

The method of querying the first 10 items in SQL is as follows:

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