How to remove not null constraint in sql server using query

I am trying to remove not null 开发者_如何学Goconstraint in sql server 2008 without losing data.

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 ALTER TABLE YourTable ALTER COLUMN YourColumn columnType NULL

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Remove constraint not null to null

ALTER TABLE 'test' CHANGE COLUMN 'testColumn' 'testColumn' datatype NULL;

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Remove column constraint: not null to null

ALTER TABLE test ALTER COLUMN column_01 DROP NOT NULL;

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Reference: https://www.tutorialspoint.com/How-can-we-remove-NOT-NULL-constraint-from-a-column-of-an-existing-MySQL-table

ALTER TABLE tableName MODIFY columnName columnType NULL;