Tables(1)

tables Tables(1)#

1️⃣ What does Tables (1) mean?#

In pgAdmin, under:

Schemas
└── public
   └── Tables (1)

Tables (1) means:

There is exactly one table inside the public schema.

In my case, that table is:

students

2️⃣ What is a Table in PostgreSQL (core concept)#

A table is:

  • A persistent storage structure

  • Stores data in rows (records) and columns (fields)

  • Enforces rules (constraints)

  • Can be secured (RLS)

  • Can be optimized (indexes)

  • Can trigger logic (triggers)

Think of a table as:

The single source of truth for your data

3️⃣ Expand students — what each child means#

When you expand:

Tables
└── students

You see:

Columns
Constraints
Indexes
RLS Policies
Rules
Triggers

Each one is not optional fluff — they are core table properties.

4️⃣ Columns — structure of the table#

students
└── Columns
Columns define:

  • What data is stored

  • Data types

  • Nullability

  • Defaults

Example:

first_name VARCHAR(100) NOT NULL

Without columns → table is meaningless.

5️⃣ Constraints — data integrity rules

students
└── Constraints

Constraints protect your data from corruption.

Examples:

  • PRIMARY KEY

  • UNIQUE

  • CHECK

  • FOREIGN KEY

Example:

email UNIQUE NOT NULL

Constraints run inside PostgreSQL, not in your app

They cannot be bypassed

6️⃣ Indexes — performance layer#

students
└── Indexes
Indexes:

  • Make queries fast

  • Are automatically created for:

  • Primary keys

  • Unique constraints

Example:

CREATE INDEX idx_students_email ON students(email);

Without indexes → slow queries at scale.

7️⃣ RLS Policies — security at row level#

students
└── RLS Policies
Row Level Security controls:

  • Who can see which rows

  • Who can modify which rows

Example idea:

student_id = current_user_id

This is zero-trust security inside PostgreSQL.

8️⃣ Rules — query rewriting (advanced, rare)#

students
└── Rules
Rules:

  • Rewrite queries before execution

  • Mostly legacy

  • Views often rely on rules internally

In modern systems:

  • Prefer triggers or views

  • Rules are rarely used directly

9️⃣ Triggers — automatic actions

students
└── Triggers
Triggers:

  • Run automatically on INSERT, UPDATE, DELETE

  • Enforce logic at DB level

Example:

  • Auto-update updated_at

  • Audit logs

  • Validation

Triggers call Trigger Functions (which you saw earlier).

🔟 Why PostgreSQL tables are powerful#

A PostgreSQL table is not just data storage.

It includes:

  • Structure (columns)

  • Integrity (constraints)

  • Performance (indexes)

  • Security (RLS)

  • Automation (triggers)

  • Logic hooks (rules)

This is why PostgreSQL can safely power:

  • APIs (PostgREST, Hasura)

  • Financial systems

  • Multi-tenant SaaS

  • Zero-trust architectures

Mental model:

A table is a mini-system, not a spreadsheet

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