How to set the data type when putting real world data into a data table

It can be created according to the length of the character, each number and space occupies the length of 1, and Chinese occupies 2 Just design by length.

For example, char(3), char(15), varchar(2), which one to use depends on your text format.

It is recommended that you take a look at the database-related tutorials, first of all, char and varchar are not the same, char(20) is a fixed-length string, varchar is a variable-length string, int, double, etc. have their own value ranges, and the definition of fields depends on the size of the data you need to store.

char is a fixed-length array, and varchar is a variable-length array. Field A ='123';char(5) = a + two spaces; varchar(5) = a;In other words, it can be changed at will depending on the actual situation of the field. memory size;

If you save text, set it to text, and if you save a document directly, you still use binary

For example, your table is user

You can start by creating a class user and putting the data in the database into the user object.

Then use the collection to store each user object, for example:

public arraylist findallusers(){arraylist al=new arraylist();

Query the database in a loop.

while(..

string name=...Find out from the database.

user user=new user();

.And so on.

return al;

Data types are acceptable.

However, floating-point, double-precision, integer, note, and general-purpose only apply to table fields.

There is nothing that cannot be used, the key is to use the most suitable one.

You search on the Internet, under the source code, I have a**.

Hope you'll find out! I know that the way to store in the database is to convert it to binary data and then write it to the database. As for saving ** as a file, it is a reverse process!

Use strings, just save the location.