framework/db/Schema.php
public function quoteSimpleColumnName($name)
    {
        if (is_string($this->tableQuoteCharacter)) {
            $startingCharacter = $endingCharacter = $this->columnQuoteCharacter;
        } else {
            list($startingCharacter, $endingCharacter) = $this->columnQuoteCharacter;
        }
        return $name === '*' || strpos($name, $startingCharacter) !== false ? $name : $startingCharacter . $name . $endingCharacter;
    }
public function quoteSimpleColumnName($name)
    {
        if (is_string($this->tableQuoteCharacter)) {
            $startingCharacter = $endingCharacter = $this->columnQuoteCharacter;
        } else {
            list($startingCharacter, $endingCharacter) = $this->columnQuoteCharacter;
        }
        return $name === '*' || strpos($name, $startingCharacter) !== false ? $name : $startingCharacter . $name . $endingCharacter;
    }
Quotes a simple column name for use in a query.
A simple column name should contain the column name only without any prefix.
If the column name is already quoted or is the asterisk character '*', this method will do nothing.
@param string $name column name
@return string the properly quoted column name