Oracle code use

When maintaining company code , It was found that ORACLE SQL To write the mapper.xml Of documents , There's a decode function , Let's learn its usage .

Here is a simple usage

decode( Name or Operation expression , Judge the condition , value 1, value 2)

If 【 Name or Operation expression 】 The value of is equal to the judgment condition , Then return the value 1, Otherwise, return the value 2. Let's take a concrete example , Suppose the table name is table：

decode(table.id,null,0,1)

The above example means table.id If null, Whole decode The value of the expression is 0, Otherwise 1. Of course , In most cases, we will use and for comparison ：

select *
from table
where decode(table.id,null,0,1)=1

That's all decode Simple usage .