system/Database/BaseBuilder.php
public function update(array $set = null, $where = null, int $limit = null, bool $test = false): bool
	{
		if ($set !== null)
		{
			$this->set($set);
		}

		if ($this->validateUpdate() === false)
		{
			return false;
		}

		if ($where !== null)
		{
			$this->where($where);
		}

		if (! empty($limit))
		{
			if (! $this->canLimitWhereUpdates)
			{
				throw new DatabaseException('This driver does not allow LIMITs on UPDATE queries using WHERE.');
			}

			$this->limit($limit);
		}

		$sql = $this->_update($this->QBFrom[0], $this->QBSet);

		if (! $test)
		{
			$this->resetWrite();

			if ($this->db->query($sql, $this->binds, false))
			{
				// Clear our binds so we don't eat up memory
				$this->binds = [];

				return true;
			}

			return false;
		}

		return true;
	}
public function update(array $set = null, $where = null, int $limit = null, bool $test = false): bool
	{
		if ($set !== null)
		{
			$this->set($set);
		}

		if ($this->validateUpdate() === false)
		{
			return false;
		}

		if ($where !== null)
		{
			$this->where($where);
		}

		if (! empty($limit))
		{
			if (! $this->canLimitWhereUpdates)
			{
				throw new DatabaseException('This driver does not allow LIMITs on UPDATE queries using WHERE.');
			}

			$this->limit($limit);
		}

		$sql = $this->_update($this->QBFrom[0], $this->QBSet);

		if (! $test)
		{
			$this->resetWrite();

			if ($this->db->query($sql, $this->binds, false))
			{
				// Clear our binds so we don't eat up memory
				$this->binds = [];

				return true;
			}

			return false;
		}

		return true;
	}
UPDATE

Compiles an update string and runs the query.

@param array   $set   An associative array of update values
@param mixed   $where
@param integer $limit
@param boolean $test  Are we testing the code?

@return boolean    TRUE on success, FALSE on failure