src/Service/DB/Select.php
protected function compileFrom()
    {
        $params = [];

        if ($this->table instanceof self) {
            list($sql, $params) = $this->table->compile();
            $table = sprintf('(%s) AS %s', $sql, $this->adapter->quoteIdentifier(uniqid()));
        } elseif ($this->table instanceof Expr) {
            $table = (string) $this->table;
        } else {
            $table = $this->adapter->quoteIdentifier($this->table);
        }

        return [$table, $params];
    }
protected function compileFrom()
    {
        $params = [];

        if ($this->table instanceof self) {
            list($sql, $params) = $this->table->compile();
            $table = sprintf('(%s) AS %s', $sql, $this->adapter->quoteIdentifier(uniqid()));
        } elseif ($this->table instanceof Expr) {
            $table = (string) $this->table;
        } else {
            $table = $this->adapter->quoteIdentifier($this->table);
        }

        return [$table, $params];
    }
把from参数编译为select 子句.

@return
array(
(string),    // from 子句
(array),     // 查询参数
)