Modify table: How to change 'Allow Nulls' attribute from not null to allow null

-- replace NVARCHAR(42) with the actual type of your column
ALTER TABLE your_table
ALTER COLUMN your_column NVARCHAR(42) NULL

Yes you can use ALTER TABLE as follows:

ALTER TABLE [table name] ALTER COLUMN [column name] [data type] NULL

Quoting from the ALTER TABLE documentation:

NULL can be specified in ALTER COLUMN to force a NOT NULL column to allow null values, except for columns in PRIMARY KEY constraints.

ALTER TABLE is right:

ALTER TABLE MyCustomers ALTER COLUMN CompanyName VARCHAR(20) NULL

For MySQL, MariaDB

ALTER TABLE [table name] MODIFY COLUMN [column name] [data type] NULL

Use MODIFY COLUMN instead of ALTER COLUMN.

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