Oracle兼容-语法-子查询无别名

1. 语法

1. greatsql> SELECT * FROM (SELECT 1 FROM DUAL), (SELECT 2 FROM DUAL);

即在子查询SQL语句中，无需加上别名而不会报语法错误。

2. 示例

1. greatsql>  SELECT * FROM (SELECT 1 FROM DUAL), (SELECT 2 FROM DUAL);
2. +---+---+
3. | 1 | 2 |
4. +---+---+
5. | 1 | 2 |
6. +---+---+

这个SQL请求如果是放在MySQL/Percona中执行，则会报告错误：

1. mysql> SELECT * FROM (SELECT 1 FROM DUAL), (SELECT 2 FROM DUAL);
2. ERROR 1248 (42000): Every derived table must have its own alias

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