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Overview

NULL means no value. In other words, it does not have any value, not equal to 0, empty string, or spaces. In Oxla, we can specify a different string as the null value in the COPY FROM statement.

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Syntax

You can define a string with any strings that will replace the null value, as shown in the syntax below: 
COPY table_name FROM 'file_path' (NULL 'string')

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Examples

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Case #1: Show Blank for NULL Value

  1. To begin with, create a CSV file called idvals.csv with a null value:
null,5 2,2 3,2
  1. In addition, create a table called idqty by specifying the column with an integer data type:
CREATE TABLE idqty (id INTEGER, quantity INTEGER);
  1. Execute the COPY FROM statement with a NULL option:
COPY idqty FROM idvals (NULL, 'null');
  1. A null value from the CSV file will be displayed in a table with an empty row that has no value, as shown below:
+------+----------+
| id   | quantity | 
+------+----------+
|      | 5        |
| 2    | 2        |
| 3    | 2        |
+------+----------+

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Case #2: Show String for NULL Value

  1. A string is represented with a double quote. In this case, we create a CSV file called idvals.csv with a null value as a string.
“null”,5 2,2 3,“null”
  1. Create a table called idqty by specifying the column with an integer data type:
CREATE TABLE idqty (id INTEGER, quantity INTEGER);
  1. Execute the COPY FROM statement with a NULL option:
COPY idqty FROM idvals (NULL, 'null');
  1. You can see that a null value from the CSV file will be displayed in a table with “null”:
+------+----------+
| id   | quantity | 
+------+----------+
| null | 5        |
| 2    | 2        |
| 3    | null     |
+------+----------+
You can specify another string to replace the null value. Such as blank, empty, invalid, etc.