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 8.3.3.2 Using the `--safe-updates' Option
 .........................................
 
 For beginners, a useful startup option is `--safe-updates' (or
 `--i-am-a-dummy', which has the same effect).  This option was
 introduced in MySQL 3.23.11.  It is helpful for cases when you might
 have issued a `DELETE FROM TBL_NAME' statement but forgotten the
 `WHERE' clause. Normally, such a statement will delete all rows from the
 table.  With `--safe-updates', you can delete rows only by specifying
 the key values that identify them. This helps prevent accidents.
 
 When you use the `--safe-updates' option, `mysql' issues the following
 statement when it connects to the MySQL server:
 
      SET SQL_SAFE_UPDATES=1,SQL_SELECT_LIMIT=1000, SQL_MAX_JOIN_SIZE=1000000;
 
  `SET' SET OPTION.
 
 The `SET' statement has the following effects:
 
    * You are not allowed to execute an `UPDATE' or `DELETE' statement
      unless you specify a key constraint in the `WHERE' clause or
      provide a `LIMIT' clause (or both).  For example:
 
           UPDATE TBL_NAME SET NOT_KEY_COLUMN=# WHERE KEY_COLUMN=#;
 
           UPDATE TBL_NAME SET NOT_KEY_COLUMN=# LIMIT 1;
 
    * All large `SELECT' results are automatically limited to 1,000 rows
      unless the statement includes a `LIMIT' clause.
 
    * Multiple-table `SELECT' statements that will probably need to
      examine more than 1,000,000 row combinations are aborted.
 
 
 To specify limits other than 1,000 and 1,000,000, you can override the
 defaults by using `--select_limit' and `--max_join_size' options:
 
      shell> mysql --safe-updates --select_limit=500 --max_join_size=10000
 

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