--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/IMPL/SQL/Schema/Constraint.pm	Fri Sep 04 19:40:23 2015 +0300
@@ -0,0 +1,87 @@
+package IMPL::SQL::Schema::Constraint;
+use strict;
+use warnings;
+
+use IMPL::lang;
+use IMPL::Const qw(:prop);
+use IMPL::declare {
+    base => [
+        'IMPL::Object' => undef,
+        'IMPL::Object::Disposable' => undef
+    ],
+    props => [
+        name => PROP_RO | PROP_DIRECT,
+        table => PROP_RO | PROP_DIRECT,
+        columns => PROP_RO | PROP_LIST
+    ]
+};
+
+my %aliases;
+
+sub CTOR {
+    my ($this,%args) = @_;
+    is( $args{table}, typeof IMPL::SQL::Schema::Table ) or
+        die new IMPL::InvalidArgumentException("table argument must be a table object");
+    $this->{$name} = $args{'name'};
+    $this->{$table} = $args{'table'};
+    $this->columns( [map { ResolveColumn($this->table,$_) } @{$args{'columns'}}] );
+}
+
+sub ResolveColumn {
+    my ($Table,$Column) = @_;
+    
+    my $cn = is($Column,'IMPL::SQL::Schema::Column') ? $Column->name : $Column;
+    
+    my $resolved = $Table->GetColumn($cn);
+    die new IMPL::InvalidOperationException("The column is not found in the table", $cn, $Table->name) if not $resolved;
+    return $resolved;
+}
+
+sub HasColumn {
+    my ($this,@Columns) = @_;
+    
+    my %Columns = map { $_, 1} @Columns;
+    
+    return scalar(grep { $Columns{$_->name} } $this->columns ) == scalar(@Columns);
+}
+
+sub uniqName {
+    my ($this) = @_;
+    return $this->{$table}->name.'_'.$this->{$name};
+}
+
+sub Dispose {
+    my ($this) = @_;
+    
+    $this->columns([]);
+    
+    delete $$this{$table};
+    
+    $this->SUPER::Dispose;
+}
+
+sub SameValue {
+    my ($this,$other) = @_;
+            
+    return 0 unless $this->columns->Count == $other->columns->Count;
+    
+    for ( my $i=0; $i < $this->columns->Count; $i++ ) {
+        return 0 unless $this->columns->[$i]->name eq $other->columns->[$i]->name;
+    }
+    
+    return 1;
+}
+
+sub ResolveAlias {
+    my ($self,$alias) = @_;
+    
+    return isclass($alias, typeof IMPL::SQL::Schema::Constraint) ? $alias : $aliases{$alias};
+}
+
+sub RegisterAlias {
+    my ($self,$alias) = @_;
+    
+    $aliases{$alias} = typeof($self);
+}
+
+1;