Mar
16

Converting MS Access to MySQL with relationships

I have used tools like MySQL Migration Toolkit (*) and Bullzip’s Access To MySQL utility, both do a excellent job but without relationships. We can spend a lot of hours to identifying and creating relationships until now:

I have write a VBA script to identify MS-Access relationships and create MySQL code with SQL-CREATE sentences, it will be useful after migration process using any free tool:

'Put this function in new/existing MS-Access module.
'
' Version History:
'
' 2014-02-09 - Seamus Casey
' a modification to Ivan's handy Access to MySQL relationship/constraint generator
'
' changes include:
'  1) skip Access system tables (TableDefAttributeEnum.dbSystemObjec)
'  2) add support for cascading updates/deletes
'
 
Public Sub printRelations()
    Dim sql, fk As String
    Dim I, J As Integer
    Dim db As Database
    Dim Table As TableDef
    Dim TableName As String
 
    ' grab a reference to this once, otherwise when we retrieve a table below,
    ' we will get an 'Object Invalid or No Longer Set' error.
    Set db = CurrentDb
 
    For I = 0 To db.Relations.Count - 1
 
        Set Table = db.TableDefs.Item(db.Relations(I).Table)
 
        If ((Table.Attributes And TableDefAttributeEnum.dbSystemObject) = 0) Then
 
           sql = "ALTER TABLE `" & db.Relations(I).ForeignTable & _
               "` ADD CONSTRAINT `" & db.Relations(I).Name & "` FOREIGN KEY ("
           fk = "("
           For J = 0 To db.Relations(I).Fields.Count - 1
               sql = sql & "`" & db.Relations(I).Fields(J).ForeignName & "` ,"
               fk = fk & "`" & db.Relations(I).Fields(J).Name & "` ,"
           Next J
 
           sql = Left(sql, Len(sql) - 1)
           fk = Left(fk, Len(fk) - 1)
           fk = fk & ")"
           sql = sql & ") REFERENCES `" & db.Relations(I).Table & "`" & fk
 
           If (db.Relations(I).Attributes And RelationAttributeEnum.dbRelationUpdateCascade) Then
               sql = sql & " ON UPDATE CASCADE"
           End If
 
           If (db.Relations(I).Attributes And RelationAttributeEnum.dbRelationDeleteCascade) Then
               sql = sql & " ON DELETE CASCADE"
           End If
 
           sql = sql & ";"
 
           Debug.Print sql
        End If
    Next I
End Sub

Gist Source

To run the adobe code go to intermediate windows (Ctrl+G) and execute: printRelations and copy the generated SQL code.

Enjoy!

(*)MySQL Migration Toolkit is discontinued but is still available from mirrors like:
http://mirrors.dotsrc.org/mysql/Downloads/MySQLGUITools/

Mar
12

MySQL must improve error messages

I just finished a database modification, a new foreign key creation  shouldn’t be take more than 5 mins, but I spent 2 hours because MySQL still have some useless error messages.

There is a way to create a new foreign key:

-- Create two tables foo and bar
CREATE TABLE foo (
	id INTEGER NOT NULL PRIMARY KEY,
	bar_id INT NOT NULL    -- foreign key
);
CREATE TABLE bar (
	id INTEGER NOT NULL PRIMARY KEY
);
-- Try to create a foreign key on `foo`
ALTER TABLE foo
	ADD FOREIGN KEY(bar_id) REFERENCES bar(SOME_FIELD) ;

The last sentence returns a generic error message:

Error Code: 1005. Can't create table 'temp.#sql-4bd7_11' (errno: 150)

Everything would have been easier if I had noticed that wrong field name bar(SOME_FIELD), sometimes happens,  but if MySQL would have shown a different message like "field bar.SOME_FIELD don't exists" I would not be awake until 2 am.

I’m using MySQL 5.5.21 community edition.

if I had noticed that wrong field name

Mar
02

Twitter bug found!

Some days ago while I’m looking for what are saying about a mysql.com server down I found a twitter bug:

Is not a big deal, to repeat this bug you must follow these steps:

1. Find any term, in this case “mysql.com” then in results looking for a word that have the search term as a part of them (ex dev.mysql.com) and select the a part or entire word:

twitter bug 01

2. Press Ctrl + C,  some HTML codes appear from nowhere:

twitter bug 02

3. Do it again and again, you will see an strange twit like this:

twitter bug 03

I’m using Firefox 8.0  under Ubuntu, but you will get the same result using Chrome and (maybe) other web clients… you can try with other searches like twitter.com and select pic.twitter.com results.

UPDATE:

@jeremycole  says: “Your URL-selection Twitter bug was fixed and shipped yesterday afternoon! Thanks!” on Mar 14 2012

Mar
01

Alias shortcuts to MySQL CLI

Do you get write laziness in the command line everything what you need to connect to a MySQL server every time?

It may take less than minute, but sometimes one minute is vital (especially if we’re near the end of the world):

ivancp@ubuntu$ mysql -u root -p -h mysqlhost database

When we are hurry, these commands often fail several times per minute.

The solution: we can create shortcuts with bash alias commands in file ~/.bashrc :

# File ~ /. Bashrc
 
# Command "my" to connect to a local server
alias my='mysql -u root -p'
 
# Command "my2" to connect to a remote server
alias my2='mysql -u root -h 192.168.1.56 -p'

Next time if you want to access the local server just type the command my [database name] , there only ask for database password. You can use any command aliases, I prefer  “my” and “my2” they are short and useful.

But if you have several servers comes another problem, how to know in which server I’m?

Open a mysql-cli can be super fast with alias shortcuts, but all terminals have the same default prompt: mysql>  To avoid disasters (ex. run DROP in wrong place) you can change mysql-cli prompt with option --prompt , then finally our .bashrc look like this:

#improved ~/.bashrc 
 
# Command "my" to connect to a local server
alias my='mysql -u root --password=secret --prompt="local> "'
 
# Command "my2" to connect to a remote server
alias my2='mysql -u root --password=secret  -h 192.168.1.56 --prompt="server 1> "'

Note I added --password parameter, it can be dangerous, use it under your own risk.

Enjoy!

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