Basic knowledge of mysql (2)

1. Sorting rules
Use ORDER BY clause to sort
ASC (ascend): ascending order
DESC (descend): descending order
ORDER BY clause in SELECTthe end of the statement.

 We can use column aliases to sortSELECT employee_id,salary,salary * 12 annual_salFROM employeesORDER BY annual_sal;#Note: Column aliases can only be used in ORDER BY, not in WHERE.#The following operation reports an error!SELECT employee_id,salary,salary * 12 annual_salFROM employeesWHERE annual_sal > 81600;

Second, paging
LIMIT is used in MySQL to implement paging
Format: LIMIT [position offset,] number of rows
#Requirement: display pageSize records per page,The pageNo page is displayed:
#Formula:
SELECT * FROM table LIMIT(PageNo - 1)*PageSize,PageSize;

Note: The LIMIT clause must be placed at the end of the entire SELECT statement!
The benefits of using LIMIT
Constraining the number of returned results can reduce the network traffic of the data table and improve query efficiency.
If we know that there is only one result returned, we can use LIMIT 1 to tell the SELECT language