MySQL and SQL >>Lesson 1: Case Sensitivity - TOP10

MySQL and SQL >>Lesson 1: Case Sensitivity


MySQL and SQL 
This section provides a tutorial introduction to MySQL by showing how to use the mysql client program to create and use a simple database. mysql (sometimes referred to as the “terminal monitor” or just “monitor”) is an interactive program that enables you to connect to a MySQL server, run queries, and view the results. mysql may also be used in batch mode: you place your queries in a file beforehand, then tell mysql to execute the contents of the file. Both ways of using mysql are covered here.
To see a list of options provided by mysql, invoke it with the --help option:  shell> mysql --help This chapter assumes that mysql is installed on your machine and that a MySQL server is available to which you can connect. If this is not true, contact your MySQL administrator. (If you are the administrator, you need to consult the relevant portions of this manual, such as MySQL Server Administration.)

As we begin using SQL and creating MySQL identifiers, we should briefly talk about case sensitivity in MySQL. SQL keywords are not case sensitive. This is standard across database systems. Case sensitivity for identifiers depends on the database system you are using. In MySQL, whether database and table names are case sensitive depends on your operating system. The reason for this is that generally each database will have an underlying directory in your operating system, and each table will have an underlying file. These directory names and filenames follow different rules depending on the operating system. What this means in practice is that if you are using Windows, database and table names are not case sensitive, but if you are using a Unix-like operating system, they are. This can be a bit of a minefield, especially when you consider that in MacOS X, you can set up your file systems to be either case insensitive (HFS+, the default,) or case sensitive (UFS).
To reduce confusion, it is good practice to treat all identifiers as case sensitive, even if you are working on a Windows system. This will allow you to move to another platform easily. Deliberately using two forms of the same identifier, such as Employee and employee, would create confusion for any humans reading the code, so this is a bad idea.
Column names, indexes, and aliases (which we will discuss later) are never case sensitive in MySQL.

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