Null null sql

Viewed k times. Community Bot 1 1 1 silver badge. Sachin Kainth Sachin Kainth Check out: w3schools. Add a comment. Active Oldest Votes. Here's some SQL showing a variety of conditions and and their effect as per above.

These, by nature, are not equal to each other. NULL is not a value, and therefore cannot be compared to another value. Curtis Curtis Null is a value, it's just unknown value.

Like in programming languages variable can have value null. Furthermore you can compare if varA! In sql though its treated differently like you pointed out. It's more of a philosophical thing though But we know so little about Dr.

Nick that the NULL values in his spouse and status columns represent an unknown value. To maintain the integrity of a database, both interpretations of NULL are necessary. Binary logic uses two values: True and False, 0 and 1, etc. Ternary logic uses three values. Interesting, but not something you need to memorize. As you will see, SQL helps us work around this tricky logic. Which is handy, because SQL comparison operations use the same ternary logic.

Whatever the comparison column contains — salaries, pet names, etc. This is true even if the column value is NULL. This is what confuses programmers who are experienced in other languages. So as our query is evaluated, it is going to look like this:. This comparison is also going to return unknown. We can see from the truth table earlier that NOT unknown is going to return unknown. So now our query has become:. The result not being false is not enough.

The value of any NULL is unknown. Again it is the unknown value of NULL. What are null values? A NULL value in a table is a value in a field that appears to be blank. A field with a NULL value is a field with no value. It is very important to understand that a NULL value is different than a zero value or a field that contains spaces. How do I make null values 0 in SQL? Add an else to your case statements so that they default to zero if the test condition is not found.

What is null in programming? In computer programming, null is both a value and a pointer. Null is a built-in constant that has a value of zero. It is the same as the character 0 used to terminate strings in C.

Null can also be the value of a pointer, which is the same as zero unless the CPU supports a special bit pattern for a null pointer.