通过迁移向列添加默认值 [英] Add a default value to a column through a migration

问题描述

如何向通过迁移已存在的列添加默认值?

How do I add a default value to a column that already exists through a migration?

我能找到的所有文档都向您展示了如果该列不存在但在这种情况下它存在时如何执行的操作.

All the documentation I can find shows you how to do it if the column doesn't already exist but in this case it does.

推荐答案

您应该这样做:

change_column :users, :admin, :boolean, :default => false

但是某些数据库(例如 PostgreSQL)不会更新先前创建的行的字段，因此请确保您也在迁移时手动更新该字段.

But some databases, like PostgreSQL, will not update the field for rows previously created, so make sure you update the field manaully on the migration too.

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