mysql not null

Differences between null and not null in mysql and efficiency issues Mysql users may encounter the following situations: 1. My field type is not null. Why can I insert null values? 2. Why is not null more efficient than null? 3. When determining

Believe that a lot of people who have been using MySQL for a long time, the concept of these two field properties is not very clear, the general will have the following questions: My field type is not NULL, why can I insert a null value

In mysql, null, not null, default, and auto_increment are common content. Here I will detail the usage of null, not null, default, and auto_increment in msyql. NULL and not null modifiers: You can add the NULL or not null modifier after each field

Mysql explores not null constraints and null values, and mysqlnull Yesterday, a front-end developer suddenly asked me a basic question: "My table columns have the not null constraint. Why can I insert null values? What's more strange is that you can

In MySQL, when you filter non-empty, you often use are not null and!=null, and these two methods are literally similar to each other, actually like It will be very different if you try to run it. Why is this happening? Null means nothing, no =, >,

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MySQL has become one of the most widely used databases on the network, especially for Web applications. it occupies the absolute advantage of small and medium applications. All of this comes from its small and easy-to-use, secure and effective, open

NULL and NOT NULL modifiers: You can add this null or NOT NULL modifier to each field to specify whether the field can be empty (null), or you must fill in the data (not NULL). mysql specifies null modifiers by default, and if a field is specified

One thousand reasons for not using Null, Null Hong Kong, Null seems to be a headache everywhere. For example, NullPointerException, which is a headache in Java, in order to avoid the unexpected Null pointer exception, for thousands of years,

In MySQL, the processing of NULL fields, it is important to note that when there is null in the processing query condition, it is possible that the value you get is not desired because, in MySQL, the null value equals (=) is judged equal (=) or