Shulou(Shulou.com)05/31 Report--

Most people do not understand the knowledge points of this article "what to pay attention to when using SQL sentences in mysql", so the editor summarizes the following contents, detailed contents, clear steps, and has a certain reference value. I hope you can get something after reading this article. Let's take a look at this "what should be paid attention to in the use of SQL sentences in mysql".

1. Prohibit the use of select*, to get only the necessary fields.

2. Insert must specify a field and prohibit the use of insert into T values ().

3. Do not replace count (*) with count (column name) or count (constant).

4. Foreign keys and cascading must not be used, and all foreign key concepts must be solved in the application layer.

Example

Note: the direct comparison between `NULL` and any value is `NULL`. 1) the returned result of `NULLNULL` is `NULL`, not `false`. 2) the returned result of `NULL` is `NULL`, not `true`. 3) the returned result of `NULL1` is `NULL`, not `true`. The above is about the content of this article on "what to pay attention to when using SQL sentences in mysql". I believe we all have a certain understanding. I hope the content shared by the editor will be helpful to you. If you want to know more related knowledge, please pay attention to the industry information channel.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.