public function getTablesUsedInFrom()
    {
        if (empty($this->from)) {
            return [];
        }

        if (is_array($this->from)) {
            $tableNames = $this->from;
        } elseif (is_string($this->from)) {
            $tableNames = preg_split('/\s*,\s*/', trim($this->from), -1, PREG_SPLIT_NO_EMPTY);
        } elseif ($this->from instanceof Expression) {
            $tableNames = [$this->from];
        } else {
            throw new InvalidConfigException(gettype($this->from) . ' in $from is not supported.');
        }

        return $this->cleanUpTableNames($tableNames);
    }
public function getTablesUsedInFrom()
    {
        if (empty($this->from)) {
            return [];
        }

        if (is_array($this->from)) {
            $tableNames = $this->from;
        } elseif (is_string($this->from)) {
            $tableNames = preg_split('/\s*,\s*/', trim($this->from), -1, PREG_SPLIT_NO_EMPTY);
        } elseif ($this->from instanceof Expression) {
            $tableNames = [$this->from];
        } else {
            throw new InvalidConfigException(gettype($this->from) . ' in $from is not supported.');
        }

        return $this->cleanUpTableNames($tableNames);
    }
Returns table names used in [[from]] indexed by aliases.
Both aliases and names are enclosed into {{ and }}.
@return string[] table names indexed by aliases
@throws \yii\base\InvalidConfigException
@since 2.0.12