在SQL中是否可以将字符串自动转换为整数？

Question

I have a SQL statement to insert a record into a table. The table is defined as;

+-------------+--------------+------+-----+---------+----------------+
| Field       | Type         | Null | Key | Default | Extra          |
+-------------+--------------+------+-----+---------+----------------+
| id          | int(11)      | NO   | PRI | NULL    | auto_increment |
| title       | varchar(255) | NO   |     | NULL    |                |
| description | text         | NO   |     | NULL    |                |
| filename    | varchar(255) | NO   |     | NULL    |                |
| type        | varchar(255) | NO   |     | NULL    |                |
| size        | int(11)      | NO   |     | NULL    |                |
+-------------+--------------+------+-----+---------+----------------+

The SQL statement is;

INSERT INTO photos 
  (title, description, filename, type, size) 
VALUES 
  ('Title D', 'Description D', 'Filename_D', 'BMP', '2000');

I was always taught that if you did not match column type to the type of data you were trying to insert or update, SQL would throw an error.

To my surprise the SQL statement worked in MySQL and MS Access even though the "size" column is defined as integer and the size data in the SQL statement is enclosed in quotes making it a string ('2000').

Is this a MySQL and MS Access feature or is this how SQL works across all SQL compliant databases?

Answer 1

String to number conversion is automatic in most databases. So, you can express your query this way:

INSERT INTO photos (title, description, filename, type, size) 
    VALUES ('Title D', 'Description D', 'Filename_D', 'BMP', '2000');

This is a bad idea, because implicit conversion can generate conversion errors -- and you have no clue where they come from. I strongly advocate using the right types or explicit conversion:

INSERT INTO photos (title, description, filename, type, size) 
    VALUES ('Title D', 'Description D', 'Filename_D', 'BMP', 2000);

Answer 2

Thank you Gordon Linoff for the answer.

Eric Brandt, I will open a fresh question on this. I'm also interested in seeing the response.