Sorting database Null values

In the process of developing a database program, you often encounter a null problem when sorting, sometimes you want null values to be in front of you, and sometimes you want to be in the back row.

This article simply records the problem of NULL ordering for Oracle and MySQL.

Sample:

Oracle Null value ordering :

Oracle provides a specialized approach to nulls first (last), which is easy to use.

Null value in front

SELECT * from Tb_test ORDER by LV nulls first

Null value in the last

SELECT * from Tb_test ORDER by LV nulls

Empty values in MySQL sort:

Null value in front

SELECT * FROM Tb_test ORDER by if (IsNull (LV), 0,1), LV

Null value in the last

SELECT * FROM Tb_test ORDER by if (IsNull (LV), 1,0), LV

All of the above are sorted by LV ascending, descending the same.

Sorting database Null values