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§ Oracle兼容-语法-子查询无别名

§ 1. 语法

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

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

greatsql>  SELECT * FROM (SELECT 1 FROM DUAL), (SELECT 2 FROM DUAL);
+---+---+
| 1 | 2 |
+---+---+
| 1 | 2 |
+---+---+
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这个SQL请求如果是放在MySQL/Percona中执行，则会报告错误：

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

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