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请点击此处查看示例表格和说明。

根据附加图像，我有三个表“PROJECTS”、“PROJECTMANAGER”和“MANAGERS”。

我需要一个查询，它可以列出由“产品”类型管理器管理的项目，这些管理器与项目状态分组。如果 STATUS=2 则显示为 Completed Projects 或 In Progress Projects。

结果表应如附图所示。期望的结果：http ://www.dbasupport.com/forums/attachment.php?attachmentid=588&d=1336691473

我需要的查询应该是通用的，以便可以在任何数据库（MySQL/Oracle/MSSQL/DB2）中使用

请帮忙。

顺便说一句，这不是作业......！！！！我使用了示例表。

我尝试过 case when 语句，但不知道如何加入并同时使用 group by。

CREATE TABLE PROJECTS 
(       
    PROJECT_ID  varchar(20), 
    PROJECT_NAME  varchar(30),
    STATUS int
);

CREATE TABLE PROJECTMANAGER
(
    PROJECT_ID  varchar(20), 
    MANAGER_ID varchar(20)
);

CREATE TABLE MANAGERS
(           
    MANAGER_ID  varchar(20), 
    MANAGER_NAME  varchar(20), 
    TYPE varchar(20)
);


INSERT INTO PROJECTS (PROJECT_ID, PROJECT_NAME, STATUS) VALUES
    ('project_001', 'Project 001', 0),
    ('project_002', 'Project 002', 1),
    ('project_003', 'Project 003', 2),
    ('project_004', 'Project 004', 0),
    ('project_005', 'Project 005', 2),
    ('project_006', 'Project 006', 0),
    ('project_007', 'Project 007', 1);


INSERT INTO PROJECTMANAGER (PROJECT_ID , MANAGER_ID) VALUES
    ('project_001', 'mgr_001'),
    ('project_002', 'mgr_001'),
    ('project_001', 'mgr_002'),
    ('project_002', 'mgr_003'),
    ('project_001', 'mgr_003'),
    ('project_005', 'mgr_001'),
    ('project_004', 'mgr_002');

INSERT INTO MANAGERS (MANAGER_ID, MANAGER_NAME, TYPE) VALUES
    ('mgr_001', 'Manager 001', 'PRODUCT'),
    ('mgr_002', 'Manager 002', 'HR'),
    ('mgr_003', 'Manager 003', 'PRODUCT'),
    ('mgr_004', 'Manager 004', 'FINANCE'),
    ('mgr_005', 'Manager 005', 'PRODUCT');



Resulted Table:

MANAGER_ID  | MANAGER _NAME | COMPLETED_PROJECTS |  IN_PROGRESS_PROJECTS |
 mgr_001    | Manager 001   |        1       |            2          |
 mgr_003    | Manager 003   |        0       |            1          |
 mgr_005    | Manager 005   |        0       |            0          |
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1 回答 1

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尝试这样的事情：

SELECT
  m.manager_id,
  m.manager_name,
  SUM(CASE WHEN p.status = 2 THEN 1 ELSE 0 END) as completed,
  SUM(CASE WHEN p.status != 2 THEN 1 ELSE 0 END) as in_progress
FROM managers m
LEFT JOIN projectmanager pm ON (m.manager_id = pm.manager_id)
LEFT JOIN projects p ON (p.project_id = pm.project_id)
WHERE m.type = 'product'
GROUP BY m.manager_id
于 2012-05-11T00:30:48.333 回答