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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

Chapter 6: MySQL Language Reference 461 In 3.23 TRUNCATE TABLE is mapped to COMMIT ; DELETE FROM table_name. See Section 6.4.6 [DELETE], page 459. TRUNCATE TABLE diers from DELETE FROM ... in the following ways: Truncate operations drop and re-create the table, which is much faster than deleting rows one by one. Not transaction-safe; you will get an error if you have an active transaction or an active table lock. Doesn't return the number of deleted rows. As long as the table denition le `table_name.frm' is valid, the table can be re-created this way, even if the data or index les have become corrupted. TRUNCATE is an Oracle SQL extension. 6.4.8 REPLACE Syntax REPLACE [LOW_PRIORITY | DELAYED] [INTO] tbl_name [(col_name,...)] VALUES (expression,...),(...),... or REPLACE [LOW_PRIORITY | DELAYED] [INTO] tbl_name [(col_name,...)] SELECT ... or REPLACE [LOW_PRIORITY | DELAYED] [INTO] tbl_name SET col_name=expression, col_name=expression,... REPLACE works exactly like INSERT, except that if an old record in the table has the same value as a new record on a UNIQUE index or PRIMARY KEY, the old record is deleted before the new record is inserted. See Section 6.4.3 [INSERT], page 454. In other words, you can't access the values of the old row from a REPLACE statement. In some old MySQL versions it appeared that you could do this, but that was a bug that has been corrected. When you use a REPLACE command, mysql_affected_rows() will return 2 if the new row replaced an old row. This is because one row was inserted and then the duplicate was deleted. This fact makes it easy to determine whether REPLACE added or replaced a row: check whether the aected-rows value is 1 (added) or 2 (replaced). Note that unless you use a UNIQUE index or PRIMARY KEY, using a REPLACE command makes no sense, since it would just do an INSERT. 6.4.9 LOAD DATA INFILE Syntax LOAD DATA [LOW_PRIORITY | CONCURRENT] [LOCAL] INFILE 'file_name.txt' [REPLACE | IGNORE] INTO TABLE tbl_name [FIELDS

MySQL Reference Manual

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