Initially, the table "MyTable" has been defined in the following way:
CREATE TABLE IF NOT EXISTS `MyTable` (
`Col1` smallint(6) NOT NULL AUTO_INCREMENT,
`Col2` smallint(6) DEFAULT NULL,
`Col3` varchar(20) NOT NULL,
);
How to update it in such a way that the column "Col 3" would be allowed to be NULL?
ALTER TABLE MyTable MODIFY Col3 varchar(20) NULL;
The following MySQL statement should modify your column to accept NULLs.
ALTER TABLE `MyTable`
ALTER COLUMN `Col3` varchar(20) DEFAULT NULL
This works in PSQL, not sure if it also works in normal SQL.
ALTER TABLE tablename
ALTER COLUMN columnname DROP NOT NULL;
ALTER TABLE school MODIFY COLUMN school_van varchar(36) DEFAULT NULL;
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