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The precedence of logical operators (`NOT`, `AND`, `OR`) determines **the order** SQL checks conditions in a `WHERE` filter.

If that order isn't set explicitly, SQL follows **its own rules**, not your intended logic.

### The standard order of precedence

1. `NOT`, evaluated first;
2. `AND`, evaluated second;
3. `OR`, evaluated last.

### An example without parentheses

```sql
SELECT * 
FROM employees
WHERE NOT city = 'Kyiv' AND department = 'IT' OR salary > 80000;
```

SQL evaluates this as:

1. First applies `NOT city = 'Kyiv'`;
2. Then checks `AND department = 'IT'`;
3. And only then `OR salary > 80000`.

That is, it selects **every IT employee not from Kyiv**
**or** everyone whose salary is over 80,000, even if they're from Kyiv and not in IT.

### How to change the precedence

To make SQL evaluate conditions in the order you want, use **parentheses**:

```sql
WHERE NOT (city = 'Kyiv' AND department = 'IT')
```

Now `NOT` applies to the whole expression inside the parentheses.

Another example:

```sql
WHERE (city = 'Kyiv' OR city = 'Lviv') AND salary > 70000;
```

The cities get checked first, then the salary filter.

### In short:

| Operator | Precedence | Usage example |
|---|---|---|
| `NOT` | 1 | `NOT city = 'Kyiv'` |
| `AND` | 2 | `age > 18 AND city = 'Kyiv'` |
| `OR` | 3 | `city = 'Kyiv' OR city = 'Lviv'` |

**Summary:**

- SQL always follows this precedence: `NOT` → `AND` → `OR`.
- To set your own order, **add parentheses**.
- It's better to always use parentheses in complex filters, it keeps the code readable and predictable.

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