Software Testing - MySQL (VI: Database Functions)

1.MySQL functions

1. Mathematical functions

PI() #Returns the value of pi (pi). The default number of decimal places is 6.

FLOOR(x) returns the largest integer less than x (rounding off decimals)

CEILING(x) rounds up

ROUND (x, y) rounds the value of the operation to y decimal places. If y is a negative number, it rounds to y decimal places.

RAND(x) returns a random number. If x is the same, the random number returned is the same.

TURNCATE(x,y) returns x with y decimal places

ABS(X) Returns the absolute value of x

MOD(X, Y) returns the remainder after dividing X by Y, even for decimals.

SQRT(x) Returns the square root of a non-negative number x.

SIGN(X) returns the sign of the parameter. If the value of x is positive, 0, or negative, it returns 1, 0, or -1 respectively.

POW(X,Y), POWER(X,Y), EXP(X) Power functions

LOG(X), LOG10(X) Logarithmic operation

RADIANS(X), DEGREES(X) functions for converting between degrees and radians

SIN(X), ASIN(X) sine function, inverse sine function

COS(X), ACOS(X) cosine and arccosine functions

2. Aggregate Functions

AVG(x) #average

COUNT(col) #Returns the number of non-controlled values ​​in a column

MIN(col) #Returns the minimum value of a column

MAX(col) #Returns the maximum value of a column

SUM(col) #Returns the sum of a column

3. String functions

CONCAT（s1,s2,s3,...）#connect strings s1,s2,s3,...

LTRIM(str) #Remove the space at the beginning of str

RTRIM(str)#Remove the space at the end of str

TRIM(str)#Remove spaces at both ends of STR

substring(str, start interception position loc, interception length len) #loc=1: first position, 2 second position

4. Date functions

YEAR(date) #Returns the year of date (1000-9999)

MONTH(data)#Returns the month of date (1-12)

DAY(data)#Return date (1-31)

HOUR(time)

MINUTE(time)

SECOND(time)

DATE(datetime)

TIME(datetime)

5. Grouping Function

as is a keyword for taking an alias, which can be omitted

select mathematical function (field name) alias, field name from indicates group by field name

#If you want to find the average score of each class

#If you use a grouping function, the fields that are not in the group must be placed after group by

The above is a detailed explanation and integration of MySQL database functions introduced by the editor. I hope it will be helpful to everyone. If you have any questions, please leave me a message and the editor will reply to you in time. I would also like to thank everyone for their support of the 123WORDPRESS.COM website!