sql-function Avg,count,max,min,sum

Common functions

AVG (average) COUNT (count) MAX (maximum value) MIN (minimum value) SUM Sum

The syntax for applying a function is:

Select from "table name";

For example, if we were to find the sum of the Sales fields from our demo table,

SELECT SUM  from Store_information;

Results:

2750

2750 represents the sum of all Sales fields: 1500 + 250 + 300 + 700.

In addition to the use of functions, SQL can also do simple mathematical operations, such as add (+) and minus (-). For the text class data, SQL also has several functions of word processing, such as text connection (concatenation), text trimming (trim), and sub-string (substring). Different databases have different syntax for these functions, so it is best to refer to the information of the database you are using to determine how these functions are used in that database.

For example, if we want to find out how many of the Store_name columns in our demo table are not blank data,

SELECT COUNT  from WHERE are not NULL;

Results:

4

COUNT and DISTINCT are often used together in order to find out how many different data are in the table (as to what is actually unimportant). For example, if we were to find out how many different store_name we had in our table, we would break in,

SELECT COUNT (DISTINCT from Store_information;

Results

3

sql-function Avg,count,max,min,sum