> ## Documentation Index
> Fetch the complete documentation index at: https://docs.dynamosql.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Expressions and Operators

> Arithmetic, bitwise, string, CASE, and conditional expressions.

## Arithmetic

Standard arithmetic with conventional precedence (`*`, `/`, `%` before `+`, `-`):

```sql theme={null}
SELECT price * quantity AS line_total FROM myschema.order_items
SELECT price * quantity - discount AS net_total FROM myschema.order_items
SELECT total % 100 AS cents_portion FROM myschema.orders
```

Unary plus and minus:

```sql theme={null}
SELECT -price AS negative_price FROM myschema.products
SELECT +total AS total FROM myschema.orders   -- unary plus is a no-op
```

## Bitwise Operators

```sql theme={null}
SELECT flags & 3 AS lower_two_bits FROM myschema.permissions  -- AND
SELECT flags | 4 AS with_flag_set FROM myschema.permissions   -- OR
SELECT flags ^ 1 AS toggled FROM myschema.permissions         -- XOR
SELECT flags << 2 AS shifted_left FROM myschema.permissions   -- left shift
SELECT flags >> 1 AS shifted_right FROM myschema.permissions  -- right shift
SELECT ~flags AS inverted FROM myschema.permissions           -- bitwise NOT
```

## String Concatenation

Use `||` to concatenate strings:

```sql theme={null}
SELECT first_name || ' ' || last_name AS full_name FROM myschema.users
SELECT 'Order #' || CAST(id AS VARCHAR) AS label FROM myschema.orders
```

## CASE

**Searched form** — each `WHEN` is a full condition:

```sql theme={null}
SELECT
  id,
  CASE
    WHEN total >= 1000 THEN 'large'
    WHEN total >= 100  THEN 'medium'
    ELSE 'small'
  END AS order_size
FROM myschema.orders
```

**Simple form** — compares a single expression against values:

```sql theme={null}
SELECT
  id,
  CASE status
    WHEN 'pending'   THEN 'Awaiting payment'
    WHEN 'shipped'   THEN 'On the way'
    WHEN 'delivered' THEN 'Complete'
    ELSE 'Unknown'
  END AS status_label
FROM myschema.orders
```

## COALESCE

Returns the first non-NULL argument:

```sql theme={null}
SELECT COALESCE(nickname, first_name, 'Anonymous') AS display_name
FROM myschema.users
```

## NULLIF

Returns NULL if both arguments are equal; otherwise returns the first argument:

```sql theme={null}
SELECT NULLIF(discount, 0) AS discount FROM myschema.orders
```

## ISNULL

Returns `true` if the argument is NULL, `false` otherwise. Equivalent to `IS NULL` in a predicate context:

```sql theme={null}
SELECT id, ISNULL(shipped_at) AS not_yet_shipped FROM myschema.orders
```

## Expression Aliases in ORDER BY

Aliases defined in `SELECT` can be used in `ORDER BY`:

```sql theme={null}
SELECT id, price * quantity AS line_total
FROM myschema.order_items
ORDER BY line_total
```

## Literals

| Type    | Example                                     |
| ------- | ------------------------------------------- |
| Integer | `42`, `-7`                                  |
| Decimal | `3.14`, `-0.5`                              |
| String  | `'hello'`, `'it''s'` (doubled single quote) |
| Boolean | `TRUE`, `FALSE`                             |
| NULL    | `NULL`                                      |

## Not Supported

* `CAST` / `CONVERT`
* `DATE`, `TIME`, `TIMESTAMP` literals
* Scientific notation literals (e.g., `1e3`)
* Hex string literals (`X'0A'`)
* Bit string literals (`B'0101'`)