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Commonly used built-in functions in mysql

小云云
小云云Original
2018-03-15 10:56:241793browse

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


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


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


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


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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