What is the difference between horizontal and vertical partitioning?

Question

Accepted Answer

**Horizontal** — split rows. **Vertical** — split columns.

**Horizontal Partitioning (Sharding):**
- Split rows across databases.
- Same schema, different data.
- Scales writes.
- Complex cross-shard queries.

```
Horizontal:
Shard 1: users 1-1000
Shard 2: users 1001-2000
(Different rows, same columns)
```

**Vertical Partitioning:**
- Split columns across databases.
- Different schema per partition.
- Scales reads.
- Simpler queries.

```
Vertical:
DB1: users (id, name, email)
DB2: user_profiles (id, bio, avatar)
(Different columns)
```

**Key differences:**
- **Horizontal** — split rows.
- **Vertical** — split columns.
- **Horizontal** — write scaling.
- **Vertical** — read scaling.

Systems Analyst: What is the difference between horizontal and vertical partitioning?