How to make a view column NOT NULL

sql

null-proofing

default-values

conditional-logic

byAnton Shumikhin·Sep 23, 2024

To ensure non-nullability in a view, encapsulate the column in COALESCE. This assigns a default value when a null is encountered:

CREATE VIEW NonNullView AS
SELECT COALESCE(maybe_null_column, 'DefaultValue') AS non_null_column
FROM source_table;

In this method, non_null_column will always hold a value, serving as a NOT NULL constraint in the context of a view.

Null-proofing a BIT column

For a BIT column, you can make it non-nullable by using an ISNULL function in combination with a default BIT value:

CREATE VIEW NonNullBitView AS
SELECT ISNULL(maybe_null_bit_column, 0) AS non_null_bit_column -- Even bits don't like null pointer exceptions 😄
FROM source_table;

This tactic ensures a BOOL-friendly default (1 or 0) that prevents null reference exceptions in the ORM or your application.

Setting up NULL-immune view for application layer

Picture this - you're dealing with NULL-phobic application code that can't deal with NULL values. Create your SQL view such that it aligns with this by making your columns non-nullable:

CREATE VIEW SafeAppView AS
SELECT 
    column1,
    ISNULL(column2, 'Fallback') AS column2, -- In case of NULL, adopt a cozy fallback value.
    CASE WHEN column3 IS NOT NULL THEN column3 ELSE 'Default' END AS column3 -- Default is the best fallback. It's the batman of fallbacks! 🦇 
FROM source_table;

By resorting to ISNULL or CASE clause, you enforce a non-nullable output, helping in preserving application stability and eliminating null reference exceptions.

Handling complex joins with non-nullable columns

For scenarios with complex joins where nulls may appear, maintaining non-nullable columns helps ensure predictable results:

CREATE VIEW JointView AS
SELECT 
  a.column1,
  ISNULL(b.column2, 0) AS column2 -- No matter how complex, zero is my hero!
FROM 
  tableA a
LEFT JOIN 
  tableB b ON a.id = b.foreign_id; -- Hope for the best, prepare for the worst! And worst is NULL. 😠

This makes sure your data model stays clean and unaltered while nulls are managed in the view output.

Powerup: Using CASE and CAST for advanced NULL handling

In complex scenarios where you want to apply conditional logic or type casting, bring in CASE and CAST:

CREATE VIEW DetailedNonNullView AS
SELECT
  column1,
  CAST(
    CASE 
      WHEN column2 > 0 THEN column2 -- Positive numbers rock!
      WHEN column2 IS NULL THEN 0 -- NULLs, not so much. Let's go with zero.
      ELSE -1 
    END AS INT
  ) AS column2 -- INT casting. Because who doesn't like a good transformation!
FROM source_table;