Question

我现在被困了好几天了。我不确定我的数据库设计效率低下还是我的查询错误。关于绩效的最佳解决方案是什么？

我有如下表格：

View:
+--------+--------------+
+ idEmpl + idDepartment +
+--------+--------------+
+ 1      + 1            +
+ 2      + 1            +
+ 3      + 2            +
+--------+--------------+

# customer is a supplier for department of employee
Table supplier:         
+--------+----------------+----------------+
+ idEmpl + idCustomer     + nrSupplier     + 
+--------+----------------+----------------+
+ 1      + 2              + 0815           +
+ 1      + 4              + 0816           +
+ 2      + 5              + 0817           +
+ 3      + 4              + 4711           +
+--------+----------------+----------------+

# customer is a manufacturer for department of employee
Table manufacturer:         
+--------+----------------+----------------+
+ idEmpl + idCustomer     + nrManufacturer + 
+--------+----------------+----------------+
+ 1      + 2              + a111           +
+ 2      + 5              + a113           +
+ 3      + 4              + b492           +
+--------+----------------+----------------+

Wanted result after query:
+--------+------------+------------+----------------+
+ idEmpl + idCustomer + nrSupplier + nrManufacturer +
+--------+------------+------------+----------------+
+ 1      + 2          + 0815       + a111           +
+ 1      + 4          + 0816       + NULL           +
+ 2      + 5          + 0816       + a112           +
+--------+------------+------------+----------------+

由于idCustomer不是员工部门的现有制造商，因此应该为NULL但我最近的查询返回＆＃39; b492＆＃39;来自员工3和他的部门2。

如果我将idDepartment添加到表供应商和制造商，我认为没有问题。但我认为不需要存储子ID，父ID。

两个查询都不会选择idDperatment = 1 ..

SELECT v.*, s.nrSupplier, m.nrManufacturer
FROM view v
LEFT JOIN supplier s     ON (v.idEmpl=s.idEmpl AND v.idDepartment=1)
LEFT JOIN manufacturer m ON (v.idEmpl=m.idEmpl AND v.idDepartment=1);

这将仅返回员工，但不会返回整个部门，供应商/制造商可能会设置不同的员工。

SELECT v.*, s.nrSupplier, m.nrManufacturer
FROM view v
LEFT JOIN supplier s     ON (v.idEmpl=s.idEmpl)
LEFT JOIN manufacturer m ON (v.idEmpl=m.idEmpl)
 WHERE v.idDepartment=1;

即使您与idDepartement

无关，仍会选择第一个找到的nrSupplier

SELECT v.*, s.nrSupplier, m.nrManufacturer
FROM view v
LEFT JOIN supplier s     ON (v.idCustomer=s.idCustomer AND vcc.idDepartment=1)
LEFT JOIN manufacturer m ON (v.idCustomer=m.idCustomer AND vcc.idDepartment=1);

Answer 1

加入manufacturer和idEmpl的{{1}}表格，以获得该结果：

idCustomer

MySQL通过父ID

1 个答案: