ModelSearch Query error in Yii2 - php

Question

I have two tables project and workload. I want show user in some project that added in Workload, and anothers member in this project (I called Team Member of that Project), too.
My idea is join 2 tables project and workload with user_id condition to take projects of user have user_id, then, from that will join with workload table again to take data from project of user have that user_id and user_id of team member will have that projects.
That my code in WorkloadSearch.php
public function searchWorkloadofUser($params) {
$user_id = Yii::$app->user->id;
$query = Workload::find()
->select(['workload.project_id', 'workload.commit_time', 'project.project_name', 'workload.from_date', 'workload.to_date', 'workload.workload_type', 'workload.comment'])
->join('INNER JOIN', 'project', 'workload.project_id=project.id')
->where('workload.user_id = '.$user_id)->orderBy('project.project_name ASC')->distinct();
$query->join('INNER JOIN','workload', 'project.id = workload.project_id')->distinct();
}
I don't understand why appeared error:
SQLSTATE[42000]: Syntax error or access violation: 1066 Not unique table/alias: 'workload'
The SQL being executed was: SELECT COUNT(*) FROM (SELECT DISTINCT `workload`.`project_id`, `workload`.`commit_time`, `project`.`project_name`, `workload`.`from_date`, `workload`.`to_date`, `workload`.`workload_type`, `workload`.`comment` FROM `workload` INNER JOIN `project` ON workload.project_id=project.id INNER JOIN `workload` ON project.id = workload.project_id WHERE workload.user_id = 20) `c`

Answer 1

like the others said: You need an alias. Your error messages tells you:
SQLSTATE[42000]: Syntax error or access violation: 1066 Not unique table/alias: 'workload'
This is beacause you joined your table worload to your workload table:
$query = Workload::find() //your `workload` table
->select([
....
])
->join('INNER JOIN', 'project p'], 'workload.project_id=p.id')
->where('workload.user_id = '.$user_id)
->orderBy('p.project_name ASC')
->distinct();
$query->join('INNER JOIN','workload', 'project.id = workload.project_id') //join the `workload` table to the `workload` table
->distinct();
When you want to join a table to itself, you have to define an alias at least for the joining table.
I would recommend you to quote the tablenames and columns whis is described in the Yii2 guide here and do not concat strings but bind params like it's described here and here. This code should work for you (not tested):
$query = Workload::find() //your `workload` table
->select([
'{{workload}}.[[project_id]]', //quoting tablenames and columns
'{{%workload}}.[[commit_time]]', //add '%' when you're using table prefix
...
])
->join('INNER JOIN', 'project p'], 'workload.project_id=p.id')
->where('workload.user_id' = :user_id, [':user_id' => $user_id]) //You should bind params when use string format
//or use hash format
//->where(['workload.user_id' => $user_id])
...
$query->join('INNER JOIN','workload w2', 'project.id = w2.project_id') //Use the alias `w2` to join the `workload` table to the `workload` table
->distinct();

Answer 2

You need to give the user table an alias the second time you join to it
e.g.
SELECT workload.project_id, workload.commit_time, p.project_name, ...
FROM workload
LEFT JOIN project p ON p.id = workload.project_id
WHERE workload.user_id = '1'
Your solution should be (untested):
public function searchWorkloadofUser($params)
{
$user_id = Yii::$app->user->id;
$query = Workload::find()
->select(['workload.project_id', 'workload.commit_time', 'p.project_name', 'workload.from_date', 'workload.to_date', 'workload.workload_type', 'workload.comment'])
->join('INNER JOIN', 'project p'], 'workload.project_id=p.id')
->where('workload.user_id = '.$user_id)->orderBy('p.project_name ASC')->distinct();
...