Oracle case when changes the queried value based on the result

First look at the table content

Select name, pass from t1;

2. Method 1: Use the decode Function

Select name, decode (pass, 'passs111', 'pass1', 'pass222', 'pass1', '', 'Password') from t1;

Note: If you do not list the possible conditions in the decode function, it is empty by default.

3. Method 2: Use the nvl Function

Select name, nvl (pass, 'password blank ') from t1;

The nvl function only assigns values when the query is null.

4. Method 3 -- Use case xxx when... then... else... end

Select name,
Case pass
When 'pass111'
Then 'mima-100'
When 'pass222'
Then 'mima-100'
Else 'mima-null'
End
From t1;

Case when else end is similar to JAVA syntax. It is best to understand what it is.