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Table of Contents
1. General Information
2. MySQL Installation
3. Tutorial Introduction
4. Database Administration
5. MySQL Optimisation
6. MySQL Language Reference
7. MySQL Table Types
8. MySQL APIs
9. Extending MySQL

380 MySQL Technical Reference for Version 4.0.3 `column_name` A column that is a keyword or contains special characters. You need not specify a tbl_name or db_name.tbl_name prex for a column reference in a statement unless the reference would be ambiguous. For example, suppose tables t1 and t2 each contain a column c, and you retrieve c in a SELECT statement that uses both t1 and t2. In this case, c is ambiguous because it is not unique among the tables used in the statement, so you must indicate which table you mean by writing t1.c or t2.c. Similarly, if you are retrieving from a table t in database db1 and from a table t in database db2, you must refer to columns in those tables as db1.t.col_name and db2.t.col_name. The syntax .tbl_name means the table tbl_name in the current database. This syntax is accepted for ODBC compatibility, because some ODBC programs prex table names with a `.' character. 6.1.3 Case Sensitivity in Names In MySQL, databases and tables correspond to directories and les within those directories. Consequently, the case-sensitivity of the underlying operating system determines the case- sensitivity of database and table names. This means database and table names are case- insensitive in Windows, and case-sensitive in most varieties of Unix (Mac OS X being an exception). See Section 1.7.3 [Extensions to ANSI], page 32. Note: although database and table names are case-insensitive for Windows, you should not refer to a given database or table using dierent cases within the same query. The following query would not work because it refers to a table both as my_table and as MY_TABLE: mysql> SELECT * FROM my_table WHERE MY_TABLE.col=1; Column names and column aliases are case-insensitive in all cases. Aliases on tables are case-sensitive. The following query would not work because it refers to the alias both as a and as A: mysql> SELECT col_name FROM tbl_name AS a -> WHERE a.col_name = 1 OR A.col_name = 2; If you have trouble remembering the lettercase for database and table names, adopt a consistent convention, such as always creating databases and tables using lowercase names. One way to avoid this problem is to start mysqld with -O lower_case_table_names=1. By default this option is 1 on Windows and 0 on Unix. If lower_case_table_names is 1 MySQL will convert all table names to lower case on storage and lookup. Note that if you change this option, you need to rst convert your old table names to lower case before starting mysqld. If you move MyISAM les from a Windows to a *nix disk, you may in some cases need to use the `mysql_fix_extensions' tool to x-up the case of the le extensions in each specied database directory (lowercase `.frm', uppercase `.MYI' and `.MYD'). `mysql_fix_extensions' can be found in the `script' subdirectory. 6.1.4 User Variables

MySQL Reference Manual

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