[Oracle] "The table has data, but the result of select COUNT (*) is 0" solution to the problem

First, the question

Today there is a magical problem-there is data in the table, but the result of select COUNT (*) is 0.

The initial manifestation of the problem is that the query report has no paging.
At first, I thought it was a Java-side problem. It was later discovered that the SQL statement that looked up the paging was returned with 0.
The SQL statement is then put into the plsql to run, and the discovery also returns 0.

The database version is Oracle 11.1.0.6.

I tried several search engines, but I couldn't find a similar situation on the Internet.

Second, there is no way to the rope

First check if the table has data--

select * from mytable

You can see that the table (mytable) does have data.

Then query the number of bars and find that the statement returns 0.

select count(*) from mytable

Change the Count method, or return 0.

select count(1) from mytableselect count(id) from mytable

Third, Vista

The number of bars can be found when the condition is added.

select count(*) from mytable where id<10

Do you want to write where you can?
What do I do if I want to check the full list of records?

So try to do this kind of writing to judge the truth, but found still return 0--

select count(*) from mytable where 1=1

It seems to be the database automatically optimized query statements.

Think again, simply instead of the primary key non-empty judgment, this is also true.

select count(*) from mytable where not id is null

This will normally find the number of records.

[Oracle] "The table has data, but the result of select COUNT (*) is 0" solution to the problem