Question

示例：

SELECT * FROM table1 WHERE $.``.age > 20

我试过以下

有效查询：

select * from table1 where $.``.age > 20

```
select * from table1 where ``.age > 20
```

select * from table1 where `table1.age` > 20

select * from table1 where $$.``.age > 20`

无效的查询

       select * from table1 where $.\`table1\`.age > 20

Answer 1

$是valid in unquoted identifiers，但就我所知，它没有任何特殊含义。您可以使用任何其他文本复制您的问题：

mysql> select *
    -> from information_schema.engines
    -> where typewhateverhere.``.transactions='YES';
+--------+---------+------------------------------------------------------------+--------------+------+------------+
| ENGINE | SUPPORT | COMMENT                                                    | TRANSACTIONS | XA   | SAVEPOINTS |
+--------+---------+------------------------------------------------------------+--------------+------+------------+
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES          | YES  | YES        |
+--------+---------+------------------------------------------------------------+--------------+------+------------+
1 row in set (0.00 sec)

我对MySQL的语法意味着什么并不是最清楚的，但是Identifier Qualifiers似乎没有记录。

MySQL中“$”的含义是什么？

1 个答案: