Altering a Column to Be Nullable

Altering a column to be nullable

Assuming SQL Server (based on your previous questions):

ALTER TABLE Merchant_Pending_Functions ALTER COLUMN NumberOfLocations INT NULL

Replace INT with your actual datatype.

Can I change a column from NOT NULL to NULL without dropping it?

ALTER TABLE myTable ALTER COLUMN myColumn {DataType} NULL

where {DataType} is the current data type of that column (For example int or varchar(10))

Altering a column: null to not null

First, make all current NULL values disappear:

UPDATE [Table] SET [Column]=0 WHERE [Column] IS NULL

Then, update the table definition to disallow "NULLs":

ALTER TABLE [Table] ALTER COLUMN [Column] INTEGER NOT NULL

How do I modify a MySQL column to allow NULL?

You want the following:

ALTER TABLE mytable MODIFY mycolumn VARCHAR(255);

Columns are nullable by default. As long as the column is not declared UNIQUE or NOT NULL, there shouldn't be any problems.

alter a table column to nullable

This came from phpmyadmin as preview SQL and it seems to work:

ALTER TABLE `other_details` CHANGE `used_asset` `used_asset` VARCHAR(100) NULL DEFAULT NULL;

Alter Column to Not Null where System Versioned column was nullable

I also looked at this and it seems you have to update the NULL values in the system version column to some value.

ALTER TABLE dbo.MyTable
    SET (SYSTEM_VERSIONING = OFF)
GO
UPDATE dbo.MyTable_History
    SET MyInt = 0 WHERE MyInt IS NULL --Update to default value
UPDATE dbo.MyTable
    SET MyInt = 0 WHERE MyInt IS NULL --Update to default value
ALTER TABLE dbo.MyTable
    ALTER COLUMN MyInt INT NOT NULL
ALTER TABLE dbo.MyTable_History
    ALTER COLUMN MyInt INT NOT NULL
GO
ALTER TABLE dbo.MyTable 
    SET (SYSTEM_VERSIONING = ON (HISTORY_TABLE = dbo.MyTable_History));
GO

How to change a PG column to NULLABLE TRUE?

From the fine manual:

ALTER TABLE mytable ALTER COLUMN mycolumn DROP NOT NULL;

There's no need to specify the type when you're just changing the nullability.

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