Add composite key demonstration using id-ego-superego

[Copilot]

Implements a composite key example using Freudian psychology concepts (id, ego, superego) to demonstrate multi-column primary keys and foreign key relationships.

Files Added

Implementation (T-Sql/id-ego-superego-composite-key.tsql, 355 lines)

• PsychologicalState table with composite PK (id, ego, superego)
• 3 child tables (PsychologicalConflict, BehavioralOutcome, PsycheMetrics) with composite FKs
• 10 sample states demonstrating unique combinations: (1,1,1), (2,1,1), (1,1,2), etc.
• Query examples: joins, CTEs, window functions, component dominance analysis

Documentation (CompositeKeys.md, 303 lines)

• When to use: junction tables, time-series, no natural single key
• Tradeoffs: semantic clarity vs join complexity
• Composite vs surrogate key comparison

Quick Reference (T-Sql/id-ego-superego-composite-key-QUICK-REFERENCE.md, 204 lines)

• ASCII diagram of table relationships
• Common patterns: exact match, joins, partial key searches

Example

-- Composite primary key
CREATE TABLE PsychologicalState (
    id INT NOT NULL,
    ego INT NOT NULL,
    superego INT NOT NULL,
    stateName VARCHAR(100),
    CONSTRAINT PK_PsychologicalState PRIMARY KEY (id, ego, superego)
);

-- Child table with composite FK
CREATE TABLE PsychologicalConflict (
    conflictId INT PRIMARY KEY IDENTITY(1,1),
    id INT NOT NULL,
    ego INT NOT NULL,
    superego INT NOT NULL,
    conflictType VARCHAR(50),
    CONSTRAINT FK_Conflict_State FOREIGN KEY (id, ego, superego)
        REFERENCES PsychologicalState(id, ego, superego)
);

-- Joining requires all key columns
SELECT ps.stateName, pc.conflictType
FROM PsychologicalState ps
JOIN PsychologicalConflict pc 
    ON ps.id = pc.id 
    AND ps.ego = pc.ego 
    AND ps.superego = pc.superego;

Individual columns are non-unique (id=1 appears in multiple rows), but combinations are unique ((1,1,1) ≠ (1,2,1) ≠ (2,1,1)).

Original prompt

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This section details on the original issue you should resolve

<issue_title>id-ego-superego as composite key</issue_title>
<issue_description></issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes id-ego-superego as composite key #55

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