Skip to main content

Case Sensitivity in String Comparisons




String comparisons are somewhat more complex than numeric or temporal comparisons. A letter in uppercase may compare as the same or different than the same letter in lowercase, and a letter with one type of accent may be considered the same or different than that letter with another type of accent.• Character Sets and Collations - String expressions contain characters from a particular character set, which is associated with one of the collations (sorting orders) available for the character set.Characters may consist of single or multiple bytes. A collation can be case insensitive (lettercase is not significant) or case sensitive (lettercase is significant).The rules that govern string comparison apply in several ways. They determine the result of comparisons performed explicitly with operators such as = and <, and comparisons performed implicitly by ORDER BY,GROUP BY, and DISTINCT operations.The default character set and collation for literal strings depend on the values of the character_set_connection and collation_connection system variables. The default character set is latin1. The default collation is latin1_swedish_ci, which is case insensitive as indicated by the “_ci” at the end of the collation name. Assuming these connection settings, literal strings
are not case sensitive by default. The comparing strings that differ only in lettercase can be seen in the following example:

mysql> SELECT 'Hello' = 'hello';
+-------------------+
| 'Hello' = 'hello' |
+-------------------+
| 1                      |
+-------------------+

A given collation might cause certain accented characters to compare the same as other characters. For example, 'ü' and 'ue' are different in the default latin1_swedish_ci collation, but with the latin1_german2_ci collation (“German phone-book” collation), they have the same sort value and thus compare as equal:

mysql> SELECT 'Müller' = 'Mueller';
+-----------------------+
| 'Müller' = 'Mueller' |
+------------------------+
| 0                             |
+------------------------+

mysql> SET collation_connection = latin1_german2_ci;
mysql> SELECT 'Müller' = 'Mueller';

+------------------------+
| 'Müller' = 'Mueller' |
+------------------------+
| 1                             |
+------------------------+




Labels:

Comments

Post a Comment

Popular posts from this blog

PHP INTRODUCTION

                     PHP  (recursive acronym for  PHP: Hypertext Preprocessor ) is a widely-used open source general-purpose scripting language that is especially suited for web development and can be embedded into HTML. PHP stands for  P HP:  H ypertext  P reprocessor PHP is a server-side scripting language, like ASP PHP scripts are executed on the server PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid, PostgreSQL, Generic ODBC, etc.) PHP is an open source software PHP is free to download and use Why PHP? PHP runs on different platforms (Windows, Linux, Unix, etc.) PHP is compatible with almost all servers used today (Apache, IIS, etc.) PHP is FREE to download from the official PHP resource:  www.php.net PHP is easy to learn and runs efficiently on the server side What can PHP do? Anything. PHP is mainly focused on server-side scripting, so you can...
6 comments
Read more

SQL Joins

1. Login in to the mysql client using the login name and password provided by your instructor (if not already logged in). 2. View the existing databases that the MySQL Server is maintaining. SHOW DATABASES; 3. Utilize the photo_album database. USE photo_album; ---- If Need be, recreate the database and load the SQL data in that will be used for this lab CREATE DATABASE photo_album; SOURCE /tmp/photo_album.sql; 4. Query the database to display the active primary customer (email, first and last name) and all the associated active login names associated with that customer. SELECT customers.email_customer, customers.fname, customers.lname, logins.login_name  FROM customers, logins WHERE customers.email_customer = logins.email_customer  AND customers.active_customer = 'True'  AND logins.active_login = 'True';
Post a Comment
Read more

Data Encryption

Data encryption is the process of scrambling stored or transmitted information so that it is unintelligible until it is unscrambled by the intended recipient. The intended recipient can then decode (or decrypt) the information. PHP offers multiple means to make this happen. However, none of these solutions are very effective without the applications running on secure servers and connections. The following are a list of the more common encryption functions in PHP: • md5() - MD5 is a third-party hash algorithm that PHP can use to create a digital fingerprint of a piece of data. It is next to impossible to (efficiently) recover the original text when a piece of data has been encrypted with the md5 hash algorithm. It is also vastly unlikely that any different text string will create an identical hash - a 'hash collision'. These properties make hashes ideally suited for storing an application's passwords because although an attacker may compromise a part of the system...
2 comments
Read more