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Displaying posts with tag: functions (reset)
Mysql: creating a link to your glossary while fetching text for a webpage

This MySql function will generate a link to your glossary when you are fetching text for a web page. All code is provided in a zip file.

MySql Lorum Ipsum generator

A short MySql function to generate a Lorum Ipsum text. You can download the code in the zip file below.

Howto generate meaningful test data using a MySQL function

You can use this MySQL function to generate names, (e-mail)addresses, phone numbers, urls, bit values, colors, IP address, etc.. As usual, the code is provided in a zip and the code is fully documented.

MySql: cleaning user input before storing the data

This article describes a single MySql function to sanitize strings. The provided options are:

  • replace multiple spaces to a single space
  • remove Unix and Windows linebreaks and replace them with a space
  • remove tabs and replace them for a single space
  • remove multiple backslashes
  • completely remove htmlentities (&)
  • replace htmlentities with the corresponding character
  • remove all HTML tags
Custom auto increment values

The auto_increment for MySQL fields are very useful but what about if I need a custom auto-increment like a custom format like 001-000033,


To make it possible we have an option based on past article MySQL Sequences:

  1. Create the table to store the current sequence values:

    CREATE TABLE _sequence
        seq_name VARCHAR(50) NOT NULL PRIMARY KEY,
        seq_group VARCHAR(10) NOT NULL,
        seq_val INT UNSIGNED NOT NULL
  2. Create a function to get and increment the current value:

    delimiter //
    DROP FUNCTION IF EXISTS getNextCustomSeq//
    CREATE FUNCTION getNextCustomSeq
        sSeqName VARCHAR(50),
        sSeqGroup VARCHAR(10)
        DECLARE nLast_val INT; 
        SET nLast_val =  (SELECT seq_val …
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Truly Random and Complex Password Generator - Part 2 of 2


In the first part of this entry, it was shown how its possible that a password from a normal user would significantly be weaker than that from a complex and randomly generated one.

Note: in the strictest sense, there is no such thing as an uncrackable password. Passwords can be uncrackable only in theory, i.e. the mathematical probability of a password being guessed correctly-- no matter how infinitesimally small the odds are, the possibility of a right guess is always present. Also, passwords are uncrackable only technically-- given enormous resources and time any password can be cracked.

Here is a function for a truly random and complex password generator which is based on …

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Truly Random and Complex Password Generator - Part 1 of 2


Skip to the 2nd part for the code snippet.

Its an important matter of security to enforce complex passwords that have a sufficient length. From personal experience, if you ask a normal user to create their own passwords, their passwords will be based on a character set consisting of 36 case-insensitive alphanumeric characters: a-z, 0-9 instead of the full 94 character set typable on all keyboard layouts. Also, most normal users would use dictionary based passwords with a predictable pattern: dictionary words at the beginning and numbers at the end.

Relying solely on the client-side or front-end to enforce the creation of passwords of at least 8 characters long and the use of …

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A better way to get Primary Key columns


When an application asks MySQL for the Primary Key of a table, there are several ways to go about doing this. A fast way would be to use these statements:

DESCRIBE `dbName`.`tableName`;
-- or
SHOW INDEX FROM `dbName`.`tableName`
WHERE `Key_name` = 'PRIMARY';

The result set would have to be parsed in order to get the column names. This is not a recommended way to get the PK columns due to its limited usefulness as the column names cannot be returned INTO a variable.

Another method often used is this SELECT statement that uses a table JOIN:

FROM `information_schema`.`TABLE_CONSTRAINTS` t
JOIN `information_schema`.`KEY_COLUMN_USAGE` k
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Safe DML Options


The Safe DML project provides automatic creation of backups and an undo functionality for MySQL. These two abilities do not rely on the command line shell and can simply be executed by queries.

$DML() Options

Inside the stored procedure, $DML(), you can find the following options that can be set:

-- Switches logging on/off
-- Clears the logs per call
-- Set to FALSE to backup only the current db in use
-- Disables filtering out of unsupported statements

  • The logging option enables/disables logs written by Safe DML into the `debug` table in …
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Safe DML


There is no native undo ability inside MySQL. Thus, the common methods to workaround the problem is through creating backup dumps and enabling binary logging, using transactions, and requiring the WHERE clause in Data Manipulation Language commands by using the safe updates option. These methods have drawbacks:

  1. Creating backups via mysqldump and using binary logging to revert to a point in time will have the same effect as an undo functionality. However, these are executed via the command line shell. Since these tools are not executed inside MySQL, this method may not be convenient and presents limitations on when it can be used.
  2. Transactions allow you to "undo" as long as you have not committed your data manipulation changes. Imagine if you discover data manipulation changes that you wish to …
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