[CONJS-131] Duplication error now indicating option checkDuplicate.

 Improvement of `checkDuplicate` option documentation

Author: rusher

documentation/connection-options.md

@@ -353,8 +353,8 @@ mariadb.createConnection({
 | **initSql** | When a connection is established, permit to execute commands before using connection|*string|array* |
 | **bulk** | disabled bulk command in batch|*boolean* |
 | **permitConnectionWhenExpired** | Permit a user with expired password to connect. Only possible operation in this case will be to change password ('SET PASSWORD=PASSWORD('XXX')')|*boolean* |false|
-| **forceVersionCheck** | Force server version check by explicitly using SELECT VERSION(), not relying on server initial packet. |*boolean* |false|
-| **checkDuplicate** | indicate to throw an exception if result-set will not contain some data due to having duplicate identifier|*boolean* | true |
+| **forceVersionCheck** | Force server version check by explicitly using SELECT VERSION(), not relying on server initial packet.<br/><i><small>Since version 2.2.0</small></i> |*boolean* |false|
+| **checkDuplicate** | Indicate to throw an exception if result-set will not contain some data due to having duplicate identifier. <br/>JSON cannot have multiple identical key, so query like `SELECT 1 as i, 2 as i` cannot result in { i:1, i:2 }, 'i:1' would be skipped. <br/>When `checkDuplicate` is enable (default) driver will throw an error if some data are skipped. Duplication error can be avoided by multiple ways, like using unique aliases or using options [`rowsAsArray`](https://github.com/mariadb-corporation/mariadb-connector-nodejs/blob/master/documentation/promise-api.md#rowsasarray) / [`nestTables`](https://github.com/mariadb-corporation/mariadb-connector-nodejs/blob/master/documentation/promise-api.md#nestTables) for example <br/><i><small>Since version 2.3.0</small></i>|*boolean* | true |
 
 
 

lib/cmd/resultset.js

@@ -283,7 +283,10 @@ class ResultSet extends Command {
             []
           );
           this.throwUnexpectedError(
-            'Error in results, duplicate field name `' + dupes[0] + '`',
+            'Error in results, duplicate field name `' +
+              dupes[0] +
+              '`.\n' +
+              '(see option `checkDuplicate`)',
             false,
             null,
             '42000',
@@ -307,7 +310,8 @@ class ResultSet extends Command {
                 this.tableHeader[i][0] +
                 '`.`' +
                 this.tableHeader[i][1] +
-                '`',
+                '`\n' +
+                '(see option `checkDuplicate`)',
               false,
               null,
               '42000',