Inner join in server side data table with php

Question

//define index of column
    $columns = array( 
        0 =>'id',
        1 =>'employee_name', 
        2 => 'employee_salary',
        3 => 'employee_age'
        4 =>'employee_City', 
        5 => 'employee_State',
        6 => 'employee_Pin'
    );

    $where = $sqlTot = $sqlRec = "";
    if( !empty($params['search']['value']) ) {   
        $where .=" WHERE ";
        $where .=" ( employee_name LIKE '".$params['search']['value']."%' ";    
        $where .=" OR employee_salary LIKE '".$params['search']['value']."%' ";

        $where .=" OR employee_age LIKE '".$params['search']['value']."%' )";
    }
    // getting total number records without any search
    $sql = "SELECT * FROM `employee` ";
    $sqlTot .= $sql;
    $sqlRec .= $sql;
    //concatenate search sql if value exist
    if(isset($where) && $where != '') {

        $sqlTot .= $where;
        $sqlRec .= $where;
    }

Help me please, I have 3 tables, all tables has a primary key as table_id how to get data from 3 tables using server side datatables how to implement join query in this code. Here employee_City, employee_State and employee_Pin are stored in second table. Employ personal details Stored in third table. How to join all tables?

Answer 1

I have just take dummy name of table city , state , pincode ..

Try with this query :

$sql = "SELECT id, employee_name, employee_salary, employee_age, employee_City, employee_State, employee_Pin FROM employee LEFT JOIN city ON employee.cityID = city.id  LEFT JOIN state ON employee.stateID = state.id  LEFT JOIN pincode ON employee.pincodeid = pincode.id  ";

  if( !empty($params['search']['value']) ) {   
        $sql .=" WHERE ";
        $sql .=" ( employee_name LIKE '%".$params['search']['value']."%' ";    
        $sql .=" OR employee_salary LIKE '%".$params['search']['value']."%' ";
        $sql .=" OR employee_age LIKE '%".$params['search']['value']."%' )";
    }
$sql.=" ORDER BY employee_name";

Answer 2

These links will help you make join query:

https://www.sitepoint.com/understanding-sql-joins-mysql-database/

http://www.techonthenet.com/mysql/joins.php