Database Mechanism

OTOBO comes with a database layer that provides access to different databases.

Kernel::System::DB supports two ways of interacting with the database: SQL and XML.


The SQL interface should be used for normal database actions (SELECT, INSERT, UPDATE, etc.). It can be used more or less like the Perl DBI interface. One limitation is that only a single statement handle may be active per database object.


my $Name        = 'Arne ßaknussemm';
my $YearOfBirth = 1662;
my $DBObject    = $Kernel::OM->Get('Kernel::System::DB');

# created
    SQL  => 'INSERT INTO alchemists (name, birth_year) VALUES ( ?, ? )',
    Bind => [ \$Name, \$YearOfBirth ],

# update
$Name =~ s/ß/S/;
    SQL  => 'UPDATE alchemists SET name = ?, birth_year = ?',
    Bind => [ \$Name, \$YearOfBirth ],

# delete
   SQL=> 'DELETE FROM alchemists WHERE birth_year > 2022',

A special feature is the possibility to insert a timestamp that is generated on the client side. Using the client time avoids inconsistences with a divergent time on the database host.

# add entry
my $Name        = 'Professor Otto Lidenbrock';
my $DBObject    = $Kernel::OM->Get('Kernel::System::DB');
    SQL  => 'INSERT INTO geologist (name, created) VALUES (?, current_timestamp)',
    Bind => [ \$Name ],

SELECT statement

my $DBObject = $Kernel::OM->Get('Kernel::System::DB');

# get the last 15 steps for transaction 123
my $TransactionNumber = 123;
my $SQL = qq{SELECT step_id FROM transaction_steps WHERE tn = ? ORDER BY step_id DESC};
    SQL   => $SQL,
    Bind  => [ \$TransactionNumber ],
    Limit => 15,

my @StepIds;
while (my @Row = $DBObject->FetchrowArray()) {
    push @StepIds, $Row[0];

# get description for all valid steps
    SQL   => q{SELECT step_id, description FROM transaction_steps WHERE valid = 1},

my %StepIdToDescription;
while (my ($StepId, $Description) = $DBObject->FetchrowArray()) {
    $StepIdToDescription{$StepId} = $Description;

# get the number of valid steps
    SQL   => q{SELECT COUNT(*) FROM transaction_steps WHERE valid = 1},

# when there is number of results is known, then no loop is required
my ($NumValid) = $DBObject->FetchrowArray();

# loops can alse be avoided with SelectAll()
# SelectAll() returns a reference to an array of array references
my @ValidIds = map { $_->[0] } $DBObject->SelectAll(
    SQL => q{SELECT DESTINCT valid_id FROM transaction_steps ORDER BY valid_id ASC},


Take care to use Limit as param and not in the SQL string because not all databases support LIMIT in SQL strings.


Use the Bind attribute whereever you can, especially for long statements. If you use Bind you do not need the function Quote().


Beware that SelectAll() may not be used within a loop over the FetchrowArray() results.



my $QuotedString = $Kernel::OM->Get('Kernel::System::DB')->Quote("It's a problem!");


my $QuotedInteger = $Kernel::OM->Get('Kernel::System::DB')->Quote('123', 'Integer');


my $QuotedNumber = $Kernel::OM->Get('Kernel::System::DB')->Quote('21.35', 'Number');


Please use the Bind attribute instead of Quote() where ever you can.


The XML interface should be used for INSERT, CREATE TABLE, DROP TABLE and ALTER TABLE. As this syntax is different from database to database, using it makes sure that you write applications that can be used in all of them.


<Insert Table="some_table">
    <Data Key="id">1</Data>
    <Data Key="description" Type="Quote">exploit</Data>


Possible data types are: BIGINT, SMALLINT, INTEGER, VARCHAR (Size=1-1000000), DATE (format: yyyy-mm-dd hh:mm:ss) and LONGBLOB.

<TableCreate Name="calendar_event">
    <Column Name="id" Required="true" PrimaryKey="true" AutoIncrement="true" Type="BIGINT"/>
    <Column Name="title" Required="true" Size="250" Type="VARCHAR"/>
    <Column Name="content" Required="false" Size="250" Type="VARCHAR"/>
    <Column Name="start_time" Required="true" Type="DATE"/>
    <Column Name="end_time" Required="true" Type="DATE"/>
    <Column Name="owner_id" Required="true" Type="INTEGER"/>
    <Column Name="event_status" Required="true" Size="50" Type="VARCHAR"/>
    <Index Name="calendar_event_title">
        <IndexColumn Name="title"/>
    <Unique Name="calendar_event_title">
        <UniqueColumn Name="title"/>
    <ForeignKey ForeignTable="users">
        <Reference Local="owner_id" Foreign="id"/>

LONGBLOB columns need special treatment. Their content needs to be base64 transcoded if the database driver does not support the feature DirectBlob. Please see the following example:

my $Content = $StorableContent;
if ( !$DBObject->GetDatabaseFunction('DirectBlob') ) {
    $Content = MIME::Base64::encode_base64($StorableContent);

Similarly, when reading from such a column, the content must not automatically be decoded as UTF-8 by passing the Encode => 0 flag to Prepare():

return if !$DBObject->Prepare(
    SQL => '
        SELECT content_type, content, content_id, content_alternative, disposition, filename
        FROM article_data_mime_attachment
        WHERE id = ?',
    Bind   => [ \$AttachmentID ],
    Encode => [ 1, 0, 0, 0, 1, 1 ],

while ( my @Row = $DBObject->FetchrowArray() ) {

    $Data{ContentType} = $Row[0];

    # Decode attachment if it's e. g. a postgresql backend.
    if ( !$DBObject->GetDatabaseFunction('DirectBlob') ) {
        $Data{Content} = decode_base64( $Row[1] );
    else {
        $Data{Content} = $Row[1];
    $Data{ContentID}          = $Row[2] || '';
    $Data{ContentAlternative} = $Row[3] || '';
    $Data{Disposition}        = $Row[4];
    $Data{Filename}           = $Row[5];


<TableDrop Name="calendar_event"/>


The following shows an example of add, change and drop columns.

<TableAlter Name="calendar_event">
    <ColumnAdd Name="test_name" Type="varchar" Size="20" Required="true"/>

    <ColumnChange NameOld="test_name" NameNew="test_title" Type="varchar" Size="30" Required="true"/>

    <ColumnChange NameOld="test_title" NameNew="test_title" Type="varchar" Size="100" Required="false"/>

    <ColumnDrop Name="test_title"/>

    <IndexCreate Name="index_test3">
        <IndexColumn Name="test3"/>

    <IndexDrop Name="index_test3"/>

    <UniqueCreate Name="uniq_test3">
        <UniqueColumn Name="test3"/>

    <UniqueDrop Name="uniq_test3"/>

The next shows an example how to rename a table.

<TableAlter NameOld="calendar_event" NameNew="calendar_event_new"/>

Code to Process XML

my @XMLARRAY = @{$Self->ParseXML(String => $XML)};

my @SQL = $Kernel::OM->Get('Kernel::System::DB')->SQLProcessor(
    Database => \@XMLARRAY,
push @SQL, $Kernel::OM->Get('Kernel::System::DB')->SQLProcessorPost();

for my $Statement (@SQL) {
    $Kernel::OM->Get('Kernel::System::DB')->Do(SQL => $Statement);

Database Drivers

The database drivers are located under $OTOBO_HOME/Kernel/System/DB/*.pm.

Supported Databases

  • MySQL or MariaDB
  • PostgreSQL
  • Oracle
  • Microsoft SQL Server (only for external database connections, not as OTOBO database)