why does "select 1 from dual" work - what is the "1"?

[R. Allan Hicks · Accepted solution]

The syntax may not make sense on first look, but if you think about it... .

1 is a literal. If you select 1 from emp; as scott/tiger, you'll see a bunch of 1's. It's similar to saying

select 'Employee Name : '||ename from emp; The string is a literal and is echoed for each row. In this case, it allows you to pretty up a report. You need the single quotes so as not to imply that you mean a column name. Since a column name of 1 is not legal, sqlplus gives you a break and assumes that it is a literal.

Hope that this helped

Dual is, as many have pointed out, a convince table, It is handy for things like select sysdate from dual;

[abc_18]

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