SCD Type

Description

Key Features

Type 1

Overwriting the existing data with new data, without keeping any history of the previous values.
直接覆盖，不留痕迹

- Overwrites Existing Data

- No Historical Data

- Simple Implementation

Type 2

Tracks historical data by creating new records for changes.

某行的一个值被修改，则在原始表上新加一行，让修改后的值成为一个独立新纪录。

- New row for each change

- Maintains full history

- Uses surrogate keys

Type 3

Adding new columns to the existing table

通过新的列来表征变化。只能记录上一次的记录

- New Columns for Historical Data

- Limited History

- Simple Structure

Type 4

Uses a separate historical table to track changes.

用独立的表用来存储历史数据。并注明change date。

- Main table holds current data

- Historical table holds old data

- Simplifies main table structure

Type 6

Combines features of Types 1, 2, and 3.

基于SCD 1,2,3，同时显示生效时间，每次的历史记录，

并多一个flag表明哪个记录是生效的。

- Maintains current and historical data

- Uses flags and effective dates

- Supports both overwriting and versioning