mysql数据库字段中 判断字段中字符类型 问题

Posted 2023-05-03

例如 `name` 字段里的字符串是 aa11 这样就判断为字符类型 如果是纯数字 1122 这样的自动判断位 数值型

sql 语句如何写呢? select * from `name` 之后如何写? 这样不知道是不是可以直接在数据库做判断,如果数据量大搜索的话 都放到数组里的话 我感觉那样效率就低很多 想知道有没有在数据库内直接判断的

您如果想要判断类型的话，可以进行转换 比如
select to_char(name) from table_name; ---这样就把您想要的数据NAME列转换为字符型;
select to_num(name) from table_name; ---这样就把您想要的数据NAME列转换为数字型;
您所说的自动判断 貌似没有 参考技术A 写个方法吧，我在ORACLE上写的
--数字返回1，字符返回0，2空值
FUNCTION F_isnot_number(parmin VARCHAR2) RETURN NUMBER IS
val NUMBER;
BEGIN
if parmin is null then
val :=2
else
val := TO_NUMBERNVL(parmin, 0);
val := 1;
end if;
RETURN val;
EXCEPTION
WHEN OTHERS THEN
val := 0;
RETURN val;
END; 参考技术B 你在建表的时候需要把每个属性的数据类型规定好。
例：
create table student_info(ID int not null primary key auto_increment, NAME varchar(20) not null, SEX varchar(1) not null, age int);

mysql的text字段长度 mysql数据库中text字段长度不够的问题

分享一下我老师大神的人工智能教程吧。零基础！通俗易懂！风趣幽默！还带黄段子！希望你也加入到我们人工智能的队伍中来！http://www.captainbed.net

类型是可变长度的字符串，最多65535个字符； 可以把字段类型改成MEDIUMTEXT（最多存放16777215个字符）或者LONGTEXT（最多存放4294967295个字符）. MySQL supports 4 TEXT field types (TINYTEXT, TEXT, MEDIUMTEXT and LONGTEXT) and this post looks at the maximum length of each of these field types. MyISAM tables in MySQL have a maximum size of a row of 65,535 bytes, so all the data in a row must fit within that limit. However, the TEXT types are stored outside the table itself and only contribute 9 to 12 bytes towards that limit. (For more information about this refer to the MySQL Manual - Data Storage Requirements chapter). TEXT data types are also able to store much more data than VARCHAR and CHAR text types so TEXT types are what you need to use when storing web page or similar content in a database. The maximum amount of data that can be stored in each data type is as follows: TINYTEXT 256 bytesTEXT 65,535 bytes ~64kb MEDIUMTEXT 16,777,215 bytes ~16MB LONGTEXT 4,294,967,295 bytes ~4GB In most circumstances the TEXT type is probably sufficient, but if you are coding a content management system it‘s probably best to use the MEDIUMTEXT type for longer pages to ensure there are no issues with data size limits.

再分享一下我老师大神的人工智能教程吧。零基础！通俗易懂！风趣幽默！还带黄段子！希望你也加入到我们人工智能的队伍中来！http://www.captainbed.net