0

If I understand correctly, the pre MySQL 5.0.3 interpretation of the BIT data type meant it could be used as a series of flags? If this is the case I can see practical uses for it in MySQL but imagine it would not have been as efficient as using SET.

Even if the above is not the case, I have great difficulty in understanding how the current implementation of the BIT data type can be practically applied in a database. If anyone is able to provide a simplified explanation and, an example of where it would be applicable, I would be grateful.

I have searched for descriptions and examples elsewhere but have been unsuccessful in finding examples applicable solely to databases.

4

1 に答える 1

0

プロパティフィールドのある行があると仮定します

として定義されたプロパティ

1  - Has property 1
2  - Has property 2
4  - Has property 3
8  - Has property 4

プロパティ1と2を割り当てます（つまり、他の1と2のみがクリーンアップされます）

 set status = status & 3

プロパティ3を追加

 set status = status | 4

プロパティ1を削除します

 set status = status | 14

プロパティ1と2の行を選択します

SELECT .. WHERE（Properties＆3）= 3

プロパティ1または2の行を選択します

SELECT .. WHERE（Properties＆1）= 1 OR（Properties＆2）= 2

于 2010-08-25T15:21:56.850 に答える