备忘:Alter Table中: ALTER vs CHANGE vs MODIFY COLUMN 区别
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三者区别在于:
ALTER COLUMN 改默认值的。
Used to set or remove the default value for a column. Example:
ALTER TABLE MyTable ALTER COLUMN foo SET DEFAULT 'bar';ALTER TABLE MyTable ALTER COLUMN foo DROP DEFAULT;
CHANGE COLUMN 包含改列名的。
Used to rename a column, change its datatype, or move it within the schema. Example:
ALTER TABLE MyTable CHANGE COLUMN foo bar VARCHAR(32) NOT NULL FIRST;ALTER TABLE MyTable CHANGE COLUMN foo bar VARCHAR(32) NOT NULL AFTER baz;
MODIFY COLUMN 不必改列名的其它修改。
Used to do everything CHANGE COLUMN can, but without renaming the column. Example:
ALTER TABLE MyTable MODIFY COLUMN foo VARCHAR(32) NOT NULL AFTER baz;
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