Question

Choose the statement that is false about NULL columns.

NULLs are ignored by aggregations

NULL is used for optional columns.

NULLs cause calculated columns to result in NULL if not handled properly

It;s best practice to make all columns NULLable its easy to conduct INSERTs and then UPDATE the row later when use have missing values

Answer 1

Answer :

NULLs cause calculated columns to result in NULL if not handled properly

Explanation :

The right sentance are

According to the SQL Reference Manual section on Aggregate Functions: All aggregate functions except COUNT(*) and GROUPING ignore nulls. You can use the NVL function in the argument to an aggregate function to substitute a value for a null. COUNT never returns null, but returns either a number or zero.

If a column in a table is optional, we can insert a new record or update an existing record without adding a value to this column. ... NULL is used as a placeholder for unknown or inapplicable values.

It is not. NULL is a non-value, a nonexistent value. It is not zero. ... As the following results show, every row includes at least one column for which no value exists: ... The ISNULL function tends to cause a bit of confusion when first encountered, ... As with numeric calculations, we must be prepared to handle ...

So NULL is used when it optional