mysql - 如果一个查询未获取数据，则 Mysql 查询不适用于连接

Question

我必须从下表中找到总库存和可用库存。表结构：

[Inventoryid] [inventory Type ] [issue status]
1              Mobile            Issued
2              Tablet            Not Issued
3              Mobile            Issued
4              Tablet            Not Issued

所需的出口是

[Inventory Type] [Total Inventory]  [Available Inventory]
Mobile            2                  0
Tablet            2                  2

请给我同样的查询。

Answer 1

SELECT  inventoryType,
        COUNT(*) totalInventory,
        SUM(issuestatus = 'not issued') available
FROM    tableName
GROUP   BY inventoryType

• SQLFiddle 演示

Answer 2

select inventory_type , count(*), sum(case when issue_Status = 'not issued' then 1
else 0 end) as status
From yourtable
group by inventory_type
;