使用Room库时遇到迁移错误：如何修改列的affinity参数？

Got it, let's figure out how to fix this affinity issue you're hitting with Room migrations.

What's Causing the Mismatch? #

First, a key SQLite quirk to note: it doesn't have a native STRING data type. When you use STRING in your ALTER TABLE statement, SQLite automatically assigns it a NUMERIC affinity (which is that affinity='1' you're seeing). But Room expects a TEXT type for Kotlin String properties, which uses TEXT affinity (affinity='2'). That's exactly where your schema mismatch is coming from.

The Simple Fix #

All you need to do is swap out STRING for TEXT in your migration SQL statement. Here's the corrected migration code:

database.execSQL("ALTER TABLE values ADD COLUMN serial_number_prefix TEXT DEFAULT null")

Why This Works #

• Using TEXT in the SQL tells SQLite to assign the correct TEXT affinity (value 2) that aligns with what Room expects for your String? property.
• Your data class code is already perfect—Room automatically maps Kotlin String? properties to TEXT columns, so no changes are needed there.

Quick Verification #

After updating the migration, Room will recognize the column's affinity as 2, matching the expected schema, and that migration error should disappear entirely.

内容的提问来源于stack exchange，提问作者Chris