信息函数
信息函数用于返回动态的数据库信息。DRDS 支持如下信息函数：
| 函数名 | 描述 |
|---|---|
| CONNECTION_ID() | Return the connection ID (thread ID) for the connection |
| CURRENT_USER(), CURRENT_USER | The authenticated user name and host name |
| DATABASE() | Return the default (current) database name |
| LAST_INSERT_ID() | Value of the AUTOINCREMENT column for the last INSERT |
| SCHEMA() | Synonym for DATABASE() |
| SESSION_USER() | Synonym for USER() |
| SYSTEM_USER() | Synonym for USER() |
| USER() | The user name and host name provided by the client |
| VERSION() | Return a string that indicates the MySQL server version |
不支持函数列表
与 MySQL5.7 相比，DRDS 暂不支持如下信息函数：
| 函数 | 描述 |
|---|---|
| BENCHMARK() | Repeatedly execute an expression |
| CHARSET() | Return the character set of the argument |
| COERCIBILITY() | Return the collation coercibility value of the string argument |
| COLLATION() | Return the collation of the string argument |
| FOUND_ROWS() | For a SELECT with a LIMIT clause, the number of rows that would be returned were there no LIMIT clause |
| ROW_COUNT() | The number of rows updated |
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