One article quick learning - playing with MySQL time operation function and detailed explanation of time matching operation + instance code

Catalog

Preface

One 、 Time plus minus

1. Time variable operation

2.date_add()

3. date_sub()

 4.period_add()

5.period_diff(P1,P2)

6.datediff(date1,date2)

 7.timediff(time1,time2)

 8.time_to_sec()、sec_to_time()

 9.to_days(date),from_days(days)

10.time_formate

  Two 、 Time format matching

1.get_format()

2.substr()

Focus , Prevent losing , If there is a mistake , Please leave a message , Thank you very much

---

---

Preface

Time is often used as a time index in a database , Changes are required during data warehousing, outbound and update . When calculating some indicators or extracting data for a certain period of time , Will operate according to the time index data in the database . Therefore, a large part of our operation data must start from the time data , But we want to really extract the time we want as an index , We also need to master many functions to facilitate our operation , This is a complicated application process .

In my blog database MySQL Three articles have explained in detail most of the functions for processing time data and the application of examples , If you have a need in this respect, you can read these three articles ：
One text speed learning - Get along well with MySQL Acquisition time 、 Detailed explanation of various operation methods for format conversion

One text speed learning - Get along well with MySQL Time selection various function operation details + The sample code

One text speed learning - Get along well with MySQL in INTERVAL Key words and INTERVAL() Function usage explanation

The first chapter details all the acquisition SQL A function of local time , And the conversion of other data types to time data types .

The second chapter details all MySQL Time data selects a function that specifies the time .

The third chapter deals with time variables interval The use and relevance of interval Usage of partition function . These three articles basically cover MySQL Time data processing and all functions obtained , Now only the time operation function and related functions are left to be explained . The above three chapters are all basic parts , And there are relevant example code displays . This blog will further explain the implementation of more complex time combination operation functions .

I hope I can help you who are reading this blog , If there are any problems that can not be solved, please put forward them in the comment area , Bloggers will answer one by one . Let's start with the text .

---

The database and tables shown above are still the same value_test form ：

 

  The fields used are generally time as well as create_time, among time In order to bigint Form storage of , and create_time In order to datetime Time type data storage .

One 、 Time plus minus

1. Time variable operation

The foregoing also describes in detail about interval How to use this keyword , Generally, it is the operation of time ：

For example, subtracting one day's time is ：

select (create_time - interval 1 day ) as times from value_test

I don't want to repeat it here , If you want to know more, you can go to the third article .

2.date_add()

date_add As the name suggests, it means to add a time interval , Basic grammar ：

date_add(< Time data >,interval < The number > < Time unit > )

The following time units and interval The type of time unit is the same , The suffix time unit has also been mentioned in the third article , There's no demo here , Here are some more complex time values based on the articles in the first three pages ：

Select the data in the total time slice from the beginning to the last seven days ：

between cast(date_sub(date_format(curdate(),'%Y%m%d') , interval 7 day)
 as DECIMAL)
 and cast(date_sub(date_format(curdate(),'%Y%m%d') , interval 1 day)
as DECIMAL)

  Select yesterday's data ：

and time= cast(date_sub(date_format(curdate(),'%Y%m%d') , interval 1 day)
 as DECIMAL)

After reading the first three articles, you should have a good understanding of the functions of applying these functions , You can add and subtract time at will .

3. date_sub()

Subtract one time interval , Here you can use interval Many time units to achieve some precise time operations .

select date_sub(create_time ,interval '1 10:10:10' day_second )
 as times from value_test

  Means to subtract 1 God 1 Hours 10 minute 10 second ：

 

You can also use date_add() Instead of , as long as interval A negative number is good .  Such as ：

select date_add(create_time ,interval '-1 10:10:10' day_second )
 as times from value_test

 4.period_add()

period_add() The basic syntax format of the function is ：

period_add(P,N)

  from add You can see that it is also an additive function ,P For the specified number of dates , and N Is the time of addition and subtraction . and date_add The difference is ,period_add No need to use interval Specify the date value , This function is based on the input P Automatically determine the unit of addition and subtraction . When the input is yyyymm when ,N It is judged as the sum of months ：

select PERIOD_ADD(202201,10) as times 

When the input is yyyymmdd when ,N Determined as days ：
 

select PERIOD_ADD(20220101,10) as times 

When using this function, you should pay attention to ,period_add Does not apply to column operations , If it is used for a column for operation, an error will be reported ：

select PERIOD_ADD(time,10) as times from value_test

 > Incorrect arguments to period_add

5.period_diff(P1,P2)

This function returns P1-P2 The time difference ,P1 and P2 It has to be for yyyymm The form of month and year , To tell you the truth, this function is almost useless , Very chicken ribs .

select PERIOD_diff(202201,202202)as times

 

6.datediff(date1,date2)

Returns the interval between two dates ：

select datediff('20220601','20220501') as time

 

  however date1 and date2 Can only be date yyyymmdd, Not in this format will be output null.

  This function can not only identify time type data , It can also work with other types of stored time data ：

select datediff(time,'20220501') as time from value_test

 

And as soon as they arrive yyyymmdd This format can be used to calculate ：

select datediff(create_time,'20220501') as time from value_test

 7.timediff(time1,time2)

Format and above datediff equally , It doesn't have any features ：

select timediff(time(create_time),'01:00:00') as time from value_test

 

 8.time_to_sec()、sec_to_time()

time_to_sec() This function can convert all the time into seconds ：

select time_to_sec(time(create_time)) as time from value_test

 

sec_to_time() This function converts seconds into time , and time_to_sec() The other way around , You can stack it again and go back to the original function ：

select sec_to_time(time_to_sec(time(create_time))) as time from value_test

 9.to_days(date),from_days(days)

to_days() Input date Date converted to days ：

select to_days(time) as time from value_test

 date The input parameter does not specify that time type data is required , Other time type formats that can be recognized by storage can be .

Its termination time is ：0000/00/00

from_days（） On the contrary , Convert days to date, Here we also use two nesting to get the original data ：

select from_days(to_days(time)) as time from value_test

 

10.time_formate

Here we make up for the omission of the time conversion function in the previous article time_format function , The usage is simple and limited to time time, And date_format The difference is ：time_format Time can be converted into 00.00.00 In the form of ：

select time_format(time(create_time),'%H.%i.%s') as time from value_test

 

 

  Two 、 Time format matching

1.get_format()

get_format() Function syntax format is ：

get_format(< Time data >,'< Specify the characters  'eur'|'usa'|'jis'|'iso'|'internal'>')

select GET_FORMAT(date,'usa' ) as time 

  Here, it is directly posted in the form of charts ：

Time type	Regional time format	Return results
date	'usa'	'%m.%d.%Y'
date	'jis'	'%Y-%m-%d'
date	'iso'	'%Y-%m-%d'
date	'eur'	'%d.%m.%Y'
date	'internal'	%Y%m%d'
datetime	'usa'	'%Y-%m-%d %H.%i.%s'
datetime	'jis'	'%Y-%m-%d %H:%i:%s'
datetime	'iso'	'%Y-%m-%d %H:%i:%s'
datetime	'eur'	'%Y-%m-%d %H.%i.%s'
datetime	'internal'	'%Y%m%d%H%i%s'
time	'usa'	'%h:%i:%s %p'
time	'jis'	'%H:%i:%s'
time	'iso'	'%H:%i:%s'
time	'eur'	'%H.%i.%s'
time	'internal'	%H%i%s'

2.substr()

Basic grammar ：

substr(string string,num start,num length);

• string： by character string ;
• start： Is the starting position ;
• length： For the length .

If we want to select the date of the current month ：

and substr(time,1,6) = substr(  cast(date_sub(date_format(curdate(),'%Y%m%d')
 , interval 1 day) as DECIMAL),1,6)

Cannot start from 0 Start , Only from 1 Start .

select time from value_test
WHERE substr(time,1,6)>'202205'
and substr(time,1,6)<'202207'

So you can choose 6 All the data of the month .

---

Focus , Prevent losing , If there is a mistake , Please leave a message , Thank you very much

That's what this issue is all about . I am a fanstuck , If you have any questions, please leave a message for discussion , See you next time .

 

Refer to the ：mysql Time function

mysql substr() The usage function