SQL总是返回false

Question

I Want to write a sql query which will should always return false.

if i write

select 1 from dual where 1=2;

nothing is returned. how can i use where 1=2 which always returns "false".

Answer 1

That's because there is nothing where 1 = 2.

select false from dual

(Substitute the value you want it to return for false.)

Answer 2

Based on the plsql and plsqldeveloper tags I have to believe you're using Oracle. As it turns out there is no BOOLEAN type in the Oracle database product, although a BOOLEAN type does exist in PL/SQL. When I find a need to include a "true or false" value in the database I'll create a CHAR(1) column and constrain it to contain only values of 'T' or 'F'; thus, if 'F' is acceptable as a "false" value you could do something like:

SELECT 'F' FROM DUAL

If you don't like 'F' you can substitute any value you'd care to choose for the 'F'.

Share and enjoy.

Answer 3

SELECT CASE WHEN 1=2 THEN 1 ELSE 0 END FROM DUAL

Answer 4

Why don't you simply use

Select 1