Query is null oracle

So you no longer need a separate "or column is null" test. Null complicates your where clause. So some people are tempted to use "magic values" instead of null for missing or not applicable information. For example, Mr. Penguin is made of fluff, not wood! You can now use standard comparison logic to find all the rows with a volume of wood less than 15 or where it doesn't apply:.

At first glance this seems to make your code simpler. But it brings complications elsewhere. For example, say you're analysing the volume of wood used in your toys. You want to find the mean, standard deviation and minimum values for this.

Only Blue Brick and Red Brick use wood. So these calculations should return 15, 7. Live SQL. Penguin', 50, , null, 10 ; insert into toys values 2, 'Blue Brick', 10, null, 10, null ; insert into toys values 3, 'Red Brick', 20, null, 20, 1 ; commit;. If expr1 contains a NULL value, then return expr3.

If the value of expr1 contains a non-NULL value, then return expr2. If they are not equal expr1 is returned. Expressions must be of the same data type, There is no implicit conversion performed. The coalesce function returns the first non-NULL value of the expressions in the list. The list must consist of at least 2 values. When a column in a table is defined there is the possibility to have a default value for this column whenever it is inserted without a value.

This is done on insert only. If you modify the default during the life of the table, the new default will be applied from that moment on. Now how do you make sure a default is applied to columns already NULL?

It can for instance be used to build a decision table. Consider the following decision table:. The column in our table just holds the code instead of the value. If we want to represent the value instead of the code we could write a query like this:. The case statement has two flavors. The simple case and the searched case. In the simple case the expression is written only once and depending on the result of this expression one of the possible cases is being used.

This can be helpful when you need to choose from a set of distinct values. In this scenario we are going to replace a null value of a field with a string.

In this scenario we are going to replace the null value of one field with value from another field or column. In this example we are going to find the distinct cities present in the city column of the table employee. We are going to use NVL because we have a null value present in the city column and we are going to replace that using NVL function as distinct function will return null also as a unique value. In this article we have seen about the definition of NVL function and its syntax.

We also saw working of the function in Oracle and later on in the article we went through various scenarios along with examples. This is a guide to Oracle NVL. Here we discuss the introduction, how NVL function work in oracle? You may also have a look at the following articles to learn more —.

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