How to recover mysql logical delete

In projects, you will generally encounter this situation: logical deletion and multi-association are not deleted

Logical deletion (soft deletion): Logical deletion is to put a deletion mark on the data to be deleted, usually Use an is_deleted field to indicate whether the row record has been deleted (or use a status field to represent the so-called "deleted" status). Logically, the data is deleted, but the data itself still exists.

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was deleted in the front-end page and is not displayed. In fact, it was not deleted in the database. , just based on the idea of ​​a status field, 0 to start, 1 to deactivate.

So logical deletion is just to change a field named status to determine whether the front-end page is displayed. The data itself has not been deleted. If you want to restore it, you only need to change the status field back.

Idea:

When writing query SQL in XML, add one more condition, the status field in the library

SELECT * FROM md_drainage_basin
<where>
  <if test="basinName != null"> and  basin_name LIKE concat('%',#{basinName},'%')</if>
  <if test="state != null">AND state = #{state}</if>
</where>
ORDER BY sort_order

Then when we provide the data to the front-end page, we must ourselves Perform the default operation in the Java code, because the front end will not pass a status code in the query. The background generates

mdDrainageBasin.setState(0);
List<MdDrainageBasin> list = mdDrainageBasinMapper.findByQuery(mdDrainageBasin);

by default and sets the status 0 to the entity class, and then queries. In this way, the front end only sees data with status 0

Logical deletion updates the status code to 1 and calls update instead of delete. However, considering the multi-table relationship, such as hanging under the basin If a watershed is logically deleted, the water system below will also be logically deleted and not displayed. At this time, it can be judged that if there is a corresponding water system under the watershed, it will not be deleted, otherwise it will be deleted

MdDrainageBasin mdDrainageBasin = mdDrainageBasinService.findById(id);
List<MdWaterSystem> list = mdWaterSystemMapper.findByWater(mdDrainageBasin.getBasinCode());
if (list.size() > 0) {
    return ResponseMsgUtil.failure();
} else {
    mdDrainageBasin.setState(1);
    mdDrainageBasinService.update(mdDrainageBasin);
    return ResponseMsgUtil.success(mdDrainageBasin);
}

According to the ID passed in from the front end, query which watershed and how many water systems there are under this watershed. If there is a water system, do not delete it. If there is no water system, delete it

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