MySQL common functions

Number function

The name of the function	do use
ABS	Find the absolute value
SQRT	Find the quadratic root
MOD	Mod
CEIL and CEILING	The two functions have the same function , All return the minimum integer no less than the parameter , That is, round up
FLOOR	Rounding down , The return value is converted to a BIGINT
RAND	Generate a 0~1 Random number between , The input integer parameter is , Used to generate repeat sequences
ROUND	Round the parameters passed
SIGN	Returns the symbol of the parameter
POW and POWER	The functions of the two functions are the same , Are the result values of the power of the passed parameters
SIN	Find the sine
ASIN	Find the inverse sine , And functions SIN They're inverse functions to each other
COS	Find the cosine
ACOS	Find the inverse cosine , And functions COS They're inverse functions to each other
TAN	Find tangent
ATAN	Find the arctangent , And functions TAN They're inverse functions to each other
COT	Find the cotangent value

String function

The name of the function	do use
LENGTH	Evaluate string length function , Returns the byte length of the string
CONCAT	Merge string functions , The return result is the string generated by the connection parameter , Parameters can make one or more
INSERT	Replace string functions
LOWER	Convert the letters in the string to lowercase
UPPER	Convert the letters in the string to uppercase
LEFT	Take the string from the left side of the word , Returns several characters to the left of the string
RIGHT	Take the string from the right word , Returns several characters to the right of the string
TRIM	Delete the spaces on the left and right of the string
REPLACE	String replacement function , Return the new string after replacement
SUBSTRING	Intercepting string , Returns a character change of a specified length starting at a specified location
REVERSE	String inversion （ The reverse ） function , Returns the string in reverse order to the original string

Date function

The name of the function	do use
CURDATE and CURRENT_DATE	The two functions work the same , Returns the date value of the current system
CURTIME and CURRENT_TIME	The two functions work the same , Returns the time value of the current system
NOW and SYSDATE	The two functions work the same , Returns the date and time values of the current system
MONTH	Get the month in the specified date
MONTHNAME	Get the English name of the month in the specified date
DAYNAME	Get the English name of the day of the week corresponding to the specified date
DAYOFWEEK	Gets the index location value of the week corresponding to the specified date
WEEK	Get the specified date is the week of the year , Whether the return value range is 0〜52 or 1〜53
DAYOFYEAR	The date of acquisition is the day of the year , The return value range is 1~366
DAYOFMONTH	Get the specified date is the day of the month , The return value range is 1~31
YEAR	Get year , The return value range is 1970〜2069
TIME_TO_SEC	Convert the time parameter to seconds
SEC_TO_TIME	Convert seconds to time , And TIME_TO_SEC They're inverse functions to each other
DATE_ADD and ADDDATE	The two functions have the same function , All add the specified time interval to the date
DATE_SUB and SUBDATE	The two functions have the same function , It's all subtracting the specified time interval from the date
ADDTIME	Time addition operation , Add the specified time... To the original time
SUBTIME	Time subtraction , Subtract the specified time from the original time
DATEDIFF	Get the interval between two dates , Returns the parameter 1 Subtract the parameter 2 Value
DATE_FORMAT	Format the specified date , Returns the value of the specified format according to the parameter
WEEKDAY	Get the corresponding working day index of the specified date in a week

Aggregate functions

The name of the function	effect
MAX	Query the maximum value of the specified column
MIN	Query the minimum value of the specified column
COUNT	Count the number of rows in the query result
SUM	Sum up , Returns the sum of the specified columns
AVG	averaging , Returns the average of the specified column data

The more you know , The more you don't know .