SQL function

SQL Definition of function ：

SQL There are many built-in functions for counting and calculation .

SQL Syntax of functions ：

SELECT function( Column name ) FROM  The name of the table 

SQL Type of function ：

stay SQL in , There are several basic types and types of functions , The basic type of function is ：

• Aggregate function
• Scalar function

1、SQL Medium Aggregate functions （ Aggregate function ） and Scalar function

2、SQL in AVG function （ You can return the average value of a numeric column ）

3、SQL Medium COUNT() function （ You can return a function that matches a specified condition ）

4、SQL Medium FIRST() function （ You can return the value of the first record in the specified field ）

5、SQL Medium LAST() function （ You can return the value of the last record in the specified field ）

6、SQL Medium MAX() function （ You can return the largest value in a column ,NULL Values are not included in the calculation ）

7、SQL Medium MIN() function （ You can return the smallest value in a column ,NULL Values are not included in the calculation ）

8、SQL Medium SUM() function （ Can return the total number of numeric columns ）

9、SQL Medium GROUP BY sentence （ Used to combine the total function （ for example ：SUM() function ）, Group result sets according to one or more columns

10、SQL Medium HAVING sentence   （ stay SQL add HAVING Clause because WHERE Keyword cannot be used with aggregate function ）

11、SQL Medium UCASE() function   （ This function converts the value of a field to uppercase ）

12、SQL Medium LCASE() function （ This function converts the value of a field to lowercase ）

13、SQL Medium MID() function （ This function can extract characters from text fields ）

14、SQL Medium LEN() function （ This function can return the length of the value in the text field ）

15、SQL Medium ROUND() function   （ This function rounds the numeric field to the specified number of decimal places ）

16、SQL Amount in NOW() function   （ This function can return the current date and time ）

17、SQL Medium FORMAT() function   （ This function can format the display of fields ）