From the course: Learning Oracle Database 19c
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What are NULL values? - Oracle Database Tutorial
From the course: Learning Oracle Database 19c
What are NULL values?
- All I'm going to talk about in this lesson is nothing. Does that make any sense? Yes it does. That's because Oracle Database 19-C supports ternary logic, true, false and nothing also known as null. Before we start talking about null, let's introduce the table called dual. The dual table is a table that anyone connected to the database can access. It has one column called dummy and it's data type is varchar2. It has one row and the value of dummy is an uppercase x. Here's how you'd use that table. Remember that any select statement must have at least the select clause and the from clause. If you just want to calculate a value or call a function but not reference any specific table, you'd use dual. And in the select statement on the slide I calculate the square root of two but I don't need to get that result from any particular table but I have to reference a table so I use dual. We're going to use the dual table in this lesson and many others. Back to the definition of null. Here is…
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