Commonly used built-in functions in mysql

This article mainly shares with you the commonly used built-in functions in MySQL, including aggregate functions, mathematical functions, string functions, etc. I hope it can help you.

1. Aggregation function

• COUNT() function: for any parameter except (*), Returns the number of rows in the selected collection that are not null values. For the parameter (*), returns the number of all rows in the collection, including rows with null values. . count(*) without WHERE is internally optimized by mysql and can return record parameters faster

• SUN( ) Function: Find the sum of the values ​​of a certain field in the table

• AVG() Function: Find the value of a certain field in the table The average value

• MAX()Function: Find the maximum value of a field in the table

• MIN()Function: Find the minimum value of a field in the table

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2. Mathematical function

• ABS()Function: Find the absolute value of a field in the table

• FLOOR()Function: Returns the largest integer less than or equal to parameter x

• RAND()Function: Returns a random number between 0~1

• TRUNCATE(x,y)Function: Returns the value of x retained to y digits after the decimal point

• SQRT(x)Function : Find the square root of parameter x

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3, string function

• UPPER(s)andUCASE(s)Function: Convert all letters in string s to uppercase letters

• LEFT(s,n)Function: Return The first n characters of string x

• ##SUBSTRING(s,n,len)Function: Starting from the nth position of s, get the string

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4. Date and time parameters

• CURDATE() and CURRENT_DATE() Function: used to get the current date

• CURTIME() and CURRENT_TIME() Function: used to get the current time

• NOW() and CURRENT_TIMESTAMP() Functions: Get the current date and time

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5. Other functions

• IF(expr,v1,v2)Function: Indicates that if the expression expr is true, v1 will be executed, otherwise v2 will be executed. (Similar to Sanmu Budget)

• IFNULL(expr,v2)Function: Indicates that if expr is not empty, return the value of the expression, otherwise return v2

• VERSION()Function: Get the version number information of the system

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