mysql 8的聚合查询

Question

我有两张桌子，津贴和薪水，

津贴表看起来像，

Id  Title       value
1   Transport   2000
2   Housing     1000
3   Housing     1000

工资表，

    id  Salary
    1   2000
    2   1000
    3   3000

对于没有住房津贴的身份证，房屋的价值应视为0，只需显示工资。如果有住房津贴，把工资和住房加起来。

我的查询没有给出正确的输出，

SELECT 
    s.id,
    CASE
        WHEN t.`Housing` = 0 THEN s.salary
    END AS Salary,
    CASE
        WHEN t.`Housing` <> 0 THEN t.Housing + s.salary
        WHEN t.`Housing` = 0 THEN  s.salary
    END AS SalaryAndHousing
FROM
    (SELECT 
        id,
            CASE
                WHEN Title = 'Housing' THEN value
                WHEN Title <> 'Housing' THEN 0
            END AS 'Housing'
    FROM
        Allowance) t
        JOIN
    Salaries s ON (t.id = s.id);

我查询的输出是，

id  Salary  SalaryAndHousing
1    2000        2000
2    null        2000
3    null        4000

看起来应该是，

   id        Salary    SalaryAndHousing
    1         2000          2000 -- 2000 + 0
    2         1000          2000 -- 1000 + 1000
    3         3000          4000 -- 1000 + 3000

[医]小提琴

Answer 1

这是非常简单的查询：

select 
    s.id,
    s.Salary,
    s.Salary + coalesce(a.value, 0) SalaryAndHousing
from Salaries s 
left join Allowance a on a.id = s.id and a.Title = 'Housing'
order by s.id;

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