Skip to main content

unique key

Introduction​

Verify that the values in a column or set of columns in a request parameter map are unique.

Example​

Assume that there is a human resources system department table with the following table structure:

CREATE TABLE `departments` (
   `dept_no` char(4) NOT NULL,
   `dept_name` varchar(40) NOT NULL,
   PRIMARY KEY (`dept_no`),
   UNIQUE KEY `dept_name` (`dept_name`)
)

Check rule constraints​

  • The department number is used as the primary key field and is unique. For more details about the primary key, see Primary Key
  • The department name dept_name is used as the unique key and is unique

Example 1: Successful request​

Add a new record with a department name that does not exist in the data table

POST http://127.0.0.1:21000
Content-Type: application/json;charset=utf-8
{
   "jsonrpc": "2.0",
   "method": "hrm.departments.add",
   "params": {
     "deptNo": "d234",
     "deptName": "Human Resources"
   },
   "id": "client-unique-request-id"
}

Response​

The response result of the above request is that the object returned after successful insertion contains the primary key name and value.

HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
{
   "jsonrpc": "2.0",
   "result": {
     "deptNo": "d234"
   },
   "id": "client-unique-request-id"
}

Example 2: Failed request--department name already exists​

Now we try to add a department record with the same name

POST http://127.0.0.1:21000
Content-Type: application/json;charset=utf-8
{
   "jsonrpc": "2.0",
   "method": "hrm.departments.add",
   "params": {
     "deptNo": "d235",
     "deptName": "Human Resources"
   },
   "id": "client-unique-request-id"
}

Response results​

HTTP/1.1 400 Bad Request
Content-Type: application/json; charset=utf-8
{
   "jsonrpc": "2.0",
   "error": {
     "code": -32600,
     "message": "checking for unique key conflicts: duplicate unique key in hrm.departments map[deptName:Human Resources]",
     "data": {
       "errorCode": "EU.Constraint.UK.Duplicated",
       "errorDetails": [
         {
           "constraint": "UniqueKeyDuplicated",
           "field": "deptName",
           "fieldValue": "Human Resources",
           "location": "hrm.departments",
           "message": "duplicate unique key in hrm.departments.dept_name Human Resources"
         }
       ],
       "errorMessage": "duplicate unique key in hrm.departments map[deptName:Human Resources]"
     }
   },
   "id": "client-unique-request-id"
}

It can be seen that dept_name is duplicated, unique key constraint verification failed, the request was intercepted, and Luwak refused to write.

Above example Tested on Luwak 1.12.9

Last updated on