Safe 6 Updates

[Práxedes Jamal]

Noneed to set SQL_SAFE_UPDATES to 0, I would really discourage it to do it that way. SAFE_UPDATES is by default on for a REASON. You can drive a car without safety belts and other things if you know what I mean ;)Just add in the WHERE clause a KEY-value that matches everything like a primary-key comparing to 0, so instead of writing:

Error Code: 1175. You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column To disable safe mode, toggle the option in Preferences -> SQL Editor and reconnect.

That worked. Well golly -- if I am always adding where key 0 to get around the safe update check, or even set SQL_SAFE_UPDATE=0, then I've lost the 'check' on my query. I might as well just turn off the option permanently. I suppose it makes deleting and updating a two step process instead of one.. but if you type fast enough and stop thinking about the key being special but rather as just a nuisance..

For beginners, a useful startup option is --safe-updates (or --i-am-a-dummy, which has the same effect). 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 deletes 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.

If you're having this problem in a stored procedure and you aren't able to use the key in the WHERE clause, you can solve this by declaring a variable that will hold the limit of the rows that should be updated and then use it in the update/delete query.

As stated in previous posts, changing the default settings of the database server will result in undesired modification of existing data due to an incorrect query on the data in a published project. Therefore, to implement such commands as stated in previous posts, it is necessary to run them in a test environment on sample data and then execute them after testing them correctly.

My suggestion is to write a WHERE conditional statement that will loop through all the rows in all conditions if an update should work for all rows in a table. For example, if the table contains an ID value, the condition ID > 0 can be used to select all rows:

First:Please make sure you want to update all records in that table because without the where clause it is dangerous to update all records in that table. It's rare time you want to update all records in the table.

most of the time you want to update specific records which should include where cluase if again you want to update all records open MySQL workbench> Edit> Preference>SQL Editor > scroll down at right and uncheck the "Safe Updates(rejects UPDATEs and DELETEs with no restrictions)".

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mysql supports input-line editing, which enables you to modify the current input line in place or recall previous input lines. For example, the left-arrow and right-arrow keys move horizontally within the current input line, and the up-arrow and down-arrow keys move up and down through the set of previously entered lines. Backspace deletes the character before the cursor and typing new characters enters them at the cursor position. To enter the line, press Enter.

On Windows, the editing key sequences are the same as supported for command editing in console windows. On Unix, the key sequences depend on the input library used to build mysql (for example, the libedit or readline library).

Documentation for the libedit and readline libraries is available online. To change the set of key sequences permitted by a given input library, define key bindings in the library startup file. This is a file in your home directory: .editrc for libedit and .inputrc for readline.

The up-arrow key enables you to recall input lines from current and previous sessions. In cases where a console is shared, this behavior may be unsuitable. mysql supports disabling the interactive history partially or fully, depending on the host platform.

On Windows, the history is stored in memory. Alt+F7 deletes all input lines stored in memory for the current history buffer. It also deletes the list of sequential numbers in front of the input lines displayed with F7 and recalled (by number) with F9. New input lines entered after you press Alt+F7 repopulate the current history buffer. Clearing the buffer does not prevent logging to the Windows Event Viewer, if the --syslog option was used to start mysql. Closing the console window also clears the current history buffer.

If you prevent the .mysql_history file from being created (see Controlling the History File) and use --histignore="*" to start the mysql client, the interactive history recall facility is disabled fully. Alternatively, if you omit the --histignore option, you can recall the input lines entered during the current session.

Windows provides APIs based on UTF-16LE for reading from and writing to the console; the mysql client for Windows is able to use these APIs. The Windows installer creates an item in the MySQL menu named MySQL command line client - Unicode. This item invokes the mysql client with properties set to communicate through the console to the MySQL server using Unicode.

To take advantage of this support manually, run mysql within a console that uses a compatible Unicode font and set the default character set to a Unicode character set that is supported for communication with the server:

Go to the console window properties, select the font tab, and choose Lucida Console or some other compatible Unicode font. This is necessary because console windows start by default using a DOS raster font that is inadequate for Unicode.

Execute mysql.exe with the --default-character-set=utf8mb4 (or utf8mb3) option. This option is necessary because utf16le is one of the character sets that cannot be used as the client character set. See Impermissible Client Character Sets.

With those changes, mysql uses the Windows APIs to communicate with the console using UTF-16LE, and communicate with the server using UTF-8. (The menu item mentioned previously sets the font and character set as just described.)

Some query results are much more readable when displayed vertically, instead of in the usual horizontal table format. Queries can be displayed vertically by terminating the query with \G instead of a semicolon. For example, longer text values that include newlines often are much easier to read with vertical output:

For beginners, a useful startup option is --safe-updates (or --i-am-a-dummy, which has the same effect). Safe-updates mode is helpful for cases when you might have issued an UPDATE or DELETE statement but forgotten the WHERE clause indicating which rows to modify. Normally, such statements update or delete all rows in the table. With --safe-updates, you can modify rows only by specifying the key values that identify them, or a LIMIT clause, or both. This helps prevent accidents. Safe-updates mode also restricts SELECT statements that produce (or are estimated to produce) very large result sets.

The --safe-updates option causes mysql to execute the following statement when it connects to the MySQL server, to set the session values of the sql_safe_updates, sql_select_limit, and max_join_size system variables:

It is possible for UPDATE and DELETE statements to produce an error in safe-updates mode even with a key specified in the WHERE clause, if the optimizer decides not to use the index on the key column:

Range access on the index cannot be used if memory usage exceeds that permitted by the range_optimizer_max_mem_size system variable. The optimizer then falls back to a table scan. See Limiting Memory Use for Range Optimization.

EXPLAIN with UPDATE and DELETE statements does not produce safe-updates errors. This enables use of EXPLAIN plus SHOW WARNINGS to see why an index is not used, which can be helpful in cases such as when a range_optimizer_max_mem_size violation or type conversion occurs and the optimizer does not use an index even though a key column was specified in the WHERE clause.

When a safe-updates error occurs, the error message includes the first diagnostic that was produced, to provide information about the reason for failure. For example, the message may indicate that the range_optimizer_max_mem_size value was exceeded or type conversion occurred, either of which can preclude use of an index.

If the mysql client loses its connection to the server while sending a statement, it immediately and automatically tries to reconnect once to the server and send the statement again. However, even if mysql succeeds in reconnecting, your first connection has ended and all your previous session objects and settings are lost: temporary tables, the autocommit mode, and user-defined and session variables. Also, any current transaction rolls back. This behavior may be dangerous for you, as in the following example where the server was shut down and restarted between the first and second statements without you knowing it:

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