EAV 从扩展值表中选择查询

Question

我必须使用以下 SQL Server 数据库结构来查询数据。模型可能是错误的；如果是这样的话，我很感激争论，所以我可以要求改变。如果没有，我需要一个查询来获取我将在下面详述的格式的选项卡式数据。

结构如下：

CLIENTS:

ClientID    ClientName
-----------------------
1           James
2           Leonard
3           Montgomery

ATTRIBUTES:

AttributeID     AttributeName
-----------------------------
1               Rank
2               Date
3               Salary
4               FileRecordsAmount

ATTRIBUTES_STRING:

ClientID    AttributeID     AttributeStringValue
1           1               Captain
2           1               Chief Surgeon
3           1               Chief Engineer

ATTRIBUTES_NUMERIC:

ClientID    AttributeID     AttributeNumericValue
1           4               187
2           4               2
3           4               10

我需要的结果如下：

RESULTS:
----------------------------------------------------------
ClientID    ClientName  Rank            FileRecordsAmount
1           James       Captain         187
2           Leonard     Chief Surgeon   2
3           Montgomery  Chief Engineer  10

我怎样才能做到这一点？

非常感谢！

编辑：这里（对我来说）具有挑战性的问题是属性是动态的......我有 5 个属性表（ATTRIBUTES_STRING、ATTRIBUTES_NUMERIC、ATTRIBUTES_DATE、ATTRIBUTES_BIT、ATTRIBUTES_INT），用户应该能够设置它自己的属性。

Answer 1

您需要一个 SQL 连接。它看起来像这样：

select 
    CLIENTS.ClientID, 
    CLIENTS.ClientName, 
    ATTRIBUTES_STRING1.AttributeStringValue as Rank, 
    ATTRIBUTES_NUMERIC2.AttributeNumericValue as FileRecordsAmount
from 
    CLIENTS,
    ATTRIBUTES ATTRIBUTES1,
    ATTRIBUTES ATTRIBUTES2,
    ATTRIBUTES_STRING ATTRIBUTES_STRING1,
    ATTRIBUTES_NUMERIC ATTRIBUTES_NUMERIC2
where CLIENTS.ClientID = ATTRIBUTES_STRING1.ClientID
and CLIENTS.ClientID = ATTRIBUTES_NUMERIC2.ClientID
and ATTRIBUTES_STRING1.AttributeID = ATTRIBUTES1.AttributeID
and ATTRIBUTES_NUMERIC2.AttributeID = ATTRIBUTES2.AttributeID
and ATTRIBUTES1.AttributeName = 'Rank'
and ATTRIBUTES2.AttributeName = 'FileRecordsAmount'
;

这里是SQL Fiddle 供参考。这是我的第一个 EAV 架构，所以我不会太相信它:)

编辑：下面提供的架构供参考：

create table CLIENTS (
    ClientID integer primary key,
    ClientName varchar(50) not null
);

insert into CLIENTS values (1,'James');
insert into CLIENTS values (2,'Leonard');
insert into CLIENTS values (3,'Montgomery');

create table ATTRIBUTES (
    AttributeID integer primary key,
    AttributeName varchar(50) not null
);

create index ATTRIBUTE_NAME_IDX on ATTRIBUTES (AttributeName);

insert into ATTRIBUTES values (1,'Rank');
insert into ATTRIBUTES values (2,'Date');
insert into ATTRIBUTES values (3,'Salary');
insert into ATTRIBUTES values (4,'FileRecordsAmount');

create table ATTRIBUTES_STRING (
    ClientID integer,
    AttributeID integer not null,
    AttributeStringValue varchar(255) not null,
    primary key (ClientID, AttributeID)
);

insert into ATTRIBUTES_STRING values (1,1,'Captain');
insert into ATTRIBUTES_STRING values (2,1,'Chief Surgeon');
insert into ATTRIBUTES_STRING values (3,1,'Chief Engineer');

create table ATTRIBUTES_NUMERIC (
    ClientID integer,
    AttributeID integer not null,
    AttributeNumericValue numeric(10, 5) not null,
    primary key (ClientID, AttributeID)
);
insert into ATTRIBUTES_NUMERIC values (1,4,187);
insert into ATTRIBUTES_NUMERIC values (2,4,2);
insert into ATTRIBUTES_NUMERIC values (3,4,10);

编辑：修改了选择，使其更容易使用额外的属性进行扩展