数据库中的多连接4表

Question

能帮我，用的是什么样的查询？

我尝试使用查询联接仍然失败，因为在'table company'中有id_contract，我需要从'table contract'获取数据

但我有个错误

警告: mysqli_fetch_array()期望参数1为mysqli_result，在

 $data = mysqli_query($connection, "SELECT * 
                                    FROM location
                                    inner join employee 
                                        on `employee`.`id_employee` = location.`id_employee`
                                    inner join company 
                                        on `company`.`id_company` =  location.`id_company`
                                    inner join contract 
                                        on `contract`.`id_contract` =  company .`id_contract`");    

​

table 1 : location
| id_location | id_employee | id_company

table 2 : employee
| id_employee | name | description

table 3 : company
| id_company | id_contract | company_name

table 4 : contract
| id_contract | first_date | end_date

我能从每个表中得到所有的数据吗？

Answer 1

此查询返回所有联接表中的所有列：

"SELECT loc.*,emp.*,cmp.*,cnt.*
                                FROM location loc
                                inner join employee emp
                                    on `employee`.`id_employee` = location.`id_employee`
                                inner join company cmp
                                    on `company`.`id_company` =  location.`id_company`
                                inner join contract cnt
                                    on `contract`.`id_contract` =  company .`id_contract`");