"Go" Oracle NULL

Turn from: null and empty string ' of Oracle '

1. Oracle treats empty string as ' null '

2, null and any value do the logical operation of the result is false, including and null itself

3. Empty string and null are NULL when judged by IS null

4, NULL, and any numeric value for mathematical operations, the result is null

5, can use | | Concatenate an empty string or null and string

Select ' A ' | | null | | ' B ' from dual; = = Result of AB

6, NULL as the parameter of the following Oracle built-in function, the result is also null
Select NVL (Length (null), -1) from dual;

Select NVL (Trim (null), -1) from dual;

Select NVL (LTrim (null), '-1 ') from dual;
Select NVL (RTrim (null), '-1 ') from dual;
Select NVL (RTrim (null, '), '-1 ') from dual;

Select NVL (Soundex (null), '-1 ') from dual;

Select NVL (SUBSTR (null,1), -1) from dual;

Select NVL (INSTR (null,1), -1) from dual;

Select NVL (replace (null, ' A ', ' B '), '-1 ') from dual;

Select NVL (min (null), '-1 ') from dual;
Select NVL (max (null), '-1 ') from dual;
Select NVL (SUM (null), '-1 ') from dual;
Select NVL (AVG (NULL), '-1 ') from dual;
Select NVL (SUM (null), '-1 ') from dual;

7, NULL as a parameter to the following Oracle built-in function, the result is not NULL:

Select Concat (' a ', null) from dual;
Select Concat (null, ' a ') from dual;
Select count (null) from dual;

8, other functions when used, you can also use the above method to test

"Go" Oracle NULL