New Sql operators, because they may come in handy

src/Sql/Operators/MiscOperators/SqlIfNullOperator.php

@@ -0,0 +1,17 @@
+<?php
+class SqlIfNullOperator extends SqlOperator
+{
+	protected $subject;
+	protected $target;
+
+	public function __construct($subject, $target)
+	{
+		$this->subject = $this->attachExpression($subject);
+		$this->target = $this->attachExpression($target);
+	}
+
+	public function getAsString()
+	{
+		return 'IFNULL (' . $this->subject->getAsString() . ', ' . $this->target->getAsString() . ')';
+	}
+}

src/Sql/Operators/UnaryOperators/SqlMaxOperator.php

@@ -0,0 +1,8 @@
+<?php
+class SqlMaxOperator extends SqlUnaryOperator
+{
+	public function getAsStringNonEmpty()
+	{
+		return 'MAX (' . $this->subject->getAsString() . ')';
+	}
+}