Create information-functions.md (pingcap#197)

* Create information-functions.md

* Address comments

* Add link for information functions

sql/README.md

@@ -54,7 +54,7 @@ TiDB supports the SQL-92 standard and is compatible with MySQL. To help you easi
     - [Cast Functions and Operators](cast-functions-and-operators.md)
     - Bit Functions and Operators
     - [Encryption and Compression Functions](encryption-and-compression-functions.md)
-    - Information Functions
+    - [Information Functions](information-functions.md)
     - JSON Functions
     - Functions Used with Global Transaction IDs
     - [Aggregate (GROUP BY) Functions](aggregate-group-by-functions.md)

sql/information-functions.md

@@ -0,0 +1,24 @@
+---
+title: Information Functions
+category: user guide
+---
+
+# Information Functions
+
+In TiDB, the usage of information functions is similar to MySQL. For more information, see [Information Functions](https://dev.mysql.com/doc/refman/5.7/en/information-functions.html).
+
+## Information Function Descriptions
+
+| Name | Description |
+|:-----|:------------|
+| [`CONNECTION_ID()`](https://dev.mysql.com/doc/refman/5.7/en/information-functions.html#function_connection-id) | Return the connection ID (thread ID) for the connection  |
+| [`CURRENT_USER()`, `CURRENT_USER`](https://dev.mysql.com/doc/refman/5.7/en/information-functions.html#function_current-user) | Return the authenticated user name and host name |
+| [`DATABASE()`](https://dev.mysql.com/doc/refman/5.7/en/information-functions.html#function_database) | Return the default (current) database name  |
+| [`FOUND_ROWS()`](https://dev.mysql.com/doc/refman/5.7/en/information-functions.html#function_found-rows) | For a `SELECT` with a `LIMIT` clause, the number of the rows that are returned if there is no `LIMIT` clause |
+| [`LAST_INSERT_ID()`](https://dev.mysql.com/doc/refman/5.7/en/information-functions.html#function_last-insert-id) | Return the value of the `AUTOINCREMENT` column for the last `INSERT`   |
+| [`SCHEMA()`](https://dev.mysql.com/doc/refman/5.7/en/information-functions.html#function_schema) | Synonym for `DATABASE()`  |
+| [`SESSION_USER()`](https://dev.mysql.com/doc/refman/5.7/en/information-functions.html#function_session-user) | Synonym for `USER()`    |
+| [`SYSTEM_USER()`](https://dev.mysql.com/doc/refman/5.7/en/information-functions.html#function_system-user) | Synonym for `USER()`   |
+| [`USER()`](https://dev.mysql.com/doc/refman/5.7/en/information-functions.html#function_user) | Return the user name and host name provided by the client    |
+| [`VERSION()`](https://dev.mysql.com/doc/refman/5.7/en/information-functions.html#function_version) | Return a string that indicates the MySQL server version   |
+| `TIDB_VERSION` | Return a string that indicates the TiDB server version |