Value of null in oracle sql

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 the searched case every case has its own expression. This can for instance be helpful when using ranges. The else clause is optional. NULL values are one of the most mind-boggling values in the Oracle database. 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;. Module 1. Introduction The table contains rows with several null values. Module 2. Post as a guest Name.

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