One way to avoid having case sensitivity properties become an issue is to pick a given lettercase for example, lowercase and always create databases and tables using names in that lettercase. The separator characters are disallowed in database and table names because databases are represented on disk by directories, and tables are represented on disk by at least one file. Quoting a name also allows it to be entirely numeric, something that is not true of unquoted names.
As a result, case sensitivity of database and table names depends on the way the operating system on that host treats filenames. The following queries are equivalent: Another factor that affects naming rules is that the server can be started in different naming modes. Windows filenames are not case sensitive, so a server running on Windows does not treat database and table names as case sensitive. You can specify an alias in any lettercase upper, lower, or mixed , but you must refer to it elsewhere in the query using the same case. MySQL's support for names that begin with a number is somewhat unusual among database systems. I should also point out that the set of features missing from MySQL continues to shrink over time. It's necessary to qualify names only when a table or database cannot be determined from context. Some people think so, but in response I'll simply observe that the lack of these capabilities in MySQL hasn't stopped large numbers of people from using it. The following statements are equivalent: Quoting a name also allows it to be entirely numeric, something that is not true of unquoted names. That would make it impossible to move the table to UNIX, because filenames on that platform cannot contain slashes. Column and index names are not case sensitive in MySQL. Aliases are case sensitive. Regardless of whether or not a database or table name is case sensitive on your system, you must refer to it using the same lettercase throughout a given query. SQL keywords and function names. A significant amount of progress has been made in improving MySQL since then, and those capabilities all have been added now. Alias names can be up to characters long. The UNIX pathname separator is disallowed on Windows and vice versa to make it easier to transfer databases and tables between servers running on different platforms. If you select a database with a USE statement, that database becomes the default database and is implicit in every unqualified table reference. One way to avoid having case sensitivity properties become an issue is to pick a given lettercase for example, lowercase and always create databases and tables using names in that lettercase. Legal characters in names. To refer to a column, there are three choices: To refer to a database, just specify its name: Names can start with any character that is legal in a name, including a digit. Aliases can be fairly arbitrary, but you should quote an alias within single or double quotes if it is a SQL keyword, is entirely numeric, or contains spaces or other special characters. For the first edition of this book, the list of missing features included transactions, subselects, foreign keys, and referential integrity.
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