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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

476 MySQL Technical Reference for Version 4.0.3 If you want to insert data in a MERGE table, you have to specify with INSERT_METHOD into with table the row should be inserted. See Section 7.2 [MERGE], page 501. This option was introduced in MySQL 4.0.0. In the created table the PRIMARY key will be placed rst, followed by all UNIQUE keys and then the normal keys. This helps the MySQL optimiser to prioritise which key to use and also more quickly detect duplicated UNIQUE keys. By using DATA DIRECTORY="directory" or INDEX DIRECTORY="directory" you can specify where the table handler should put it's table and index les. Note that the directory should be a full path to the directory (not relative path). This only works for MyISAM tables in MySQL 4.0, when you are not using the --skip- symlink option. See Section 5.6.1.2 [Symbolic links to tables], page 374. 6.5.3.1 Silent Column Specication Changes In some cases, MySQL silently changes a column specication from that given in a CREATE TABLE statement. (This may also occur with ALTER TABLE.): VARCHAR columns with a length less than four are changed to CHAR. If any column in a table has a variable length, the entire row is variable-length as a result. Therefore, if a table contains any variable-length columns (VARCHAR, TEXT, or BLOB), all CHAR columns longer than three characters are changed to VARCHAR columns. This doesn't aect how you use the columns in any way; in MySQL, VARCHAR is just a dierent way to store characters. MySQL performs this conversion because it saves space and makes table operations faster. See Chapter 7 [Table types], page 494. TIMESTAMP display sizes must be even and in the range from 2 to 14. If you specify a display size of 0 or greater than 14, the size is coerced to 14. Odd-valued sizes in the range from 1 to 13 are coerced to the next higher even number. You cannot store a literal NULL in a TIMESTAMP column; setting it to NULL sets it to the current date and time. Because TIMESTAMP columns behave this way, the NULL and NOT NULL attributes do not apply in the normal way and are ignored if you specify them. DESCRIBE tbl_name always reports that a TIMESTAMP column may be assigned NULL values. MySQL maps certain column types used by other SQL database vendors to MySQL types. See Section 6.2.5 [Other-vendor column types], page 404. If you want to see whether MySQL used a column type other than the one you specied, issue a DESCRIBE tbl_name statement after creating or altering your table. Certain other column type changes may occur if you compress a table using myisampack. See Section 7.1.2.3 [Compressed format], page 499. 6.5.4 ALTER TABLE Syntax ALTER [IGNORE] TABLE tbl_name alter_spec [, alter_spec ...]

MySQL Reference Manual

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