I am using MySQL data base with Rails. I have created a field of type
string. Are there any limits to its length? What about type
text is variable sized, I believe there would be extra costs associated with using text objects. How important can they get, if at all?
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A fixed-length string that is always right-padded with spaces to the specified length when stored The range of Length is 1 to 255 characters. Trailing spaces are removed when the value is retrieved.
CHARvalues are sorted and compared in case-insensitive fashion according to the default character set unless the
BINARYkeyword is given.
A variable-length string. Note: Trailing spaces are removed when the value is stored (this differs from the ANSI SQL specification)
The range of Length is 1 to 255 characters.
VARCHARvalues are sorted and compared in case-insensitive fashion unless the
BINARYkeyword is given
TINYTEXTcolumn with a maximum length of 255 (28 – 1) characters
TEXTcolumn with a maximum length of 65,535 (216 – 1) characters , bytes = 64 KiB
MEDIUMTEXTcolumn with a maximum length of 16,777,215 (224 – 1)characters , bytes = 16 MiB
LONGTEXTcolumn with a maximum length of 4,294,967,295 (232 – 1) characters , bytes = 4 GiB
See MySQL Data Types Quick Reference Table for more info.
also you can see MYSQL – String Type Overview
String, in general, should be used for short text. For example, it is a
VARCHAR(255) under MySQL.
Text uses the larger text from the database, like, in MySQL, the type
For information on how this works and the internals in MySQL and limits and such, see the other answer by Pekka.
If you are requesting, say, a paragraph, I would use text. If you are requesting a username or email, use string.
See the mySQL manual on String Types.
Values in VARCHAR columns are variable-length strings. The length can be specified as a value from 0 to 255 before MySQL 5.0.3, and 0 to 65,535 in 5.0.3 and later versions. The effective maximum length of a VARCHAR in MySQL 5.0.3 and later is subject to the maximum row size (65,535 bytes, which is shared among all columns) and the character set used.
Text: See storage requirements
If you want a fixed size text field, use
CHAR which can be 255 characters in length maximum.
TEXT both have variable length.