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How to Insert Null to Certain Columns In Oracle?

2 minutes read

To insert null values into specific columns in Oracle, you can simply omit those columns from your INSERT statement. If the column allows null values and is not specified in the INSERT statement, it will automatically be set to NULL. Alternatively, you can explicitly set a column to NULL by using the keyword NULL in the corresponding value position in the INSERT statement. This will override any default values or constraints set for that column.


What is the default behavior of sequences with null values in Oracle?

In Oracle, by default, null values are treated as last in an ascending sequence and first in a descending sequence. This means that if a sequence contains null values, they will be ordered after all non-null values when the sequence is sorted in ascending order. Similarly, in descending order, null values will come first before all non-null values.


What is the behavior of null values in comparison operations in Oracle?

In Oracle, when comparing a null value with another value using comparison operators such as =, <, >, <=, >=, or <>:

  1. NULL is not equal to any value, including NULL itself. So if you compare a null value with any other value, the result is always FALSE.
  2. Any comparison involving a NULL value will result in NULL, which is considered as unknown.
  3. When using the IS NULL or IS NOT NULL operators to compare a NULL value, the result will be TRUE or FALSE respectively.


For example:

  • SELECT NULL = 5; -- This will return FALSE
  • SELECT NULL < 10; -- This will return NULL
  • SELECT NULL IS NULL; -- This will return TRUE
  • SELECT NULL IS NOT NULL; -- This will return FALSE


It is important to handle NULL values appropriately in Oracle queries to ensure that the results are accurate and as expected.


How to set a specific column to null in Oracle?

To set a specific column to null in Oracle, you can use an update statement with the SET clause to assign NULL to the column.


Here's an example syntax to set a specific column to null:

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UPDATE table_name
SET column_name = NULL
WHERE condition;


In this syntax:

  • table_name: the name of the table you want to update
  • column_name: the name of the specific column you want to set to null
  • condition: the condition that specifies which rows to update (optional, if you want to update specific rows)


For example, if you have a table called "employees" and you want to set the "salary" column to null for all employees with a department_id of 10, you can use the following query:

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UPDATE employees
SET salary = NULL
WHERE department_id = 10;


This will set the "salary" column to null for all employees with a department_id of 10 in the "employees" table.

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