如果MySQL中的值为null，则将default插入not null列中？
您可以使用ISNULL属性IFNULL()或简单IF()的ISNULL属性。语法如下-
INSERT INTO yourTableName(yourColumnName1,yourColumnName2)
VALUES('yourValue’',IF(yourColumnName1 IS NULL,DEFAULT(yourColumnName2),'yourMessage'));为了理解上述语法，让我们创建一个表。创建表的查询如下-
mysql> create table Post -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> UserName varchar(10), -> UserPostMessage varchar(50) NOT NULL DEFAULT 'Hi Good Morning !!!' -> );
现在，如果值为null，则可以将default插入到notnull列中。查询如下-
mysql> insert into Post(UserName,UserPostMessage)
-> values('John',if(UserName IS NULL,DEFAULT(UserPostMessage),'Hello'));
mysql> insert into Post(UserName,UserPostMessage)
-> values(NULL,if(UserName IS NULL,DEFAULT(UserPostMessage),'Hello'));
mysql> insert into Post(UserName,UserPostMessage)
-> values('Carol',if(UserName IS NULL,DEFAULT(UserPostMessage),'Hello'));使用select语句显示表中的所有记录。查询如下-
mysql> select *from Post;
以下是输出-
+----+----------+---------------------+ | Id | UserName | UserPostMessage | +----+----------+---------------------+ | 1 | John | Hello | | 2 | NULL | Hi Good Morning !!! | | 3 | Carol | Hello | +----+----------+---------------------+ 3 rows in set (0.00 sec)