Question

我有两张表employees, salary_advance。

employees表格列empid, name, salary，salary_advance列id, empid, amount, date

我想显示所有员工的名字，工资，剩余...

remaining = ( salary - amount )

当我进行内部联系时，我只会让那些提前工作的员工......

我想表明谁先前和员工中的其他员工..

这是我的SQL语句

select 
    employees.name , employees.salary , 
    (employees.salary - salary_advance.amount ) 
from 
    employees 
inner join 
    salary_advance on employees.empid = salary_advance.empid

Answer 1

您需要使用LEFT OUTER JOIN代替INNER JOIN，并且您还需要使用ISNULL从NULL获取0而不是salary_advance SELECT employees.name, employees.salary, Remaining = (employees.salary - ISNULL(salary_advance.amount, 0) ) FROM employees LEFT OUTER JOIN salary_advance ON employees.empid = salary_advance.empid表：

{{1}}

Answer 2

如果员工可以有多个预付款，则您需要使用LEFT JOIN SUM和GROUP BY来获得正确的结果。如果您只需要计算某个日期以来的预付款，请将其添加到ON的{{1}}子句中;

LEFT JOIN

An SQLfiddle to test with

Answer 3

使用左连接，并处理空值：

select
  e.name , e.salary,
  employees.salary - isnull(a.amount, 0)
from
  employees e
left outer join
  salary_advance a on e.empid = a.empid

isnull函数可能被命名为ifnull，具体取决于您使用的数据库。

Answer 4

您也可以使用：

SELECT
    employees.name, 
    employees.salary, 
    ( CASE salary_advance.amount 
          WHEN NULL THEN employees.salary
          ELSE employees.salary - salary_advance.amount
      END  
    ) Remaining
FROM 
    employees 
LEFT OUTER JOIN 
    salary_advance ON employees.empid = salary_advance.empid

Answer 5

试试这个：

select 
    employees.name , employees.salary , 
    Remaining = (employees.salary - ISNULL(salary_advance.amount, 0))
from 
    employees 
left join 
    salary_advance on employees.empid = salary_advance.empid

LEFT JOIN关键字返回左表中的所有行，右表中包含匹配的行。

Answer 6

打印此：

select
    employees.name, 
    employees.salary, 
    Remaining = (employees.salary - ISNULL(salary_advance.amount, 0) ) 
from
    employees 
left outer join
    salary_advance on employees.empid = salary_advance.empid

而不是：

select 
    employees.name , employees.salary , 
    (employees.salary - salary_advance.amount ) 
from 
    employees 
inner join 
    salary_advance on employees.empid = salary_advance.empid

摘要：您需要使用left outer join代替inner join

从两个表中选择的SQL语句

6 个答案: