---
title: "sign"
slug: "dev-database-reference-sql-functions-numeric-sign"
updated: 2026-10-30T18:18:51Z
published: 2026-10-30T18:18:51Z
canonical: "docs.vastdata.com/dev-database-reference-sql-functions-numeric-sign"
---

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

# sign

*Applies to VAST Cluster 5.5.*

*[Functions](/develop/docs/dev-database-reference-sql-functions-index) › [Numeric and math functions](/develop/docs/dev-database-reference-sql-functions-numeric) › Sign and rounding.* Returns `-1` for a negative number, `0` for zero and `1` for a positive number, as a `TINYINT`.

## Syntax

```
sign(x)
```

| Argument | Type | Description |
| --- | --- | --- |
| `x` | any number: the signed and unsigned integer types, `DECIMAL`, `FLOAT` or `DOUBLE` | The value to test. |

**Returns:** `TINYINT`: `-1`, `0` or `1`.

## Set up the examples

The examples connect with the ADBC driver, as in [VAST Query Engine (ADBC)](/develop/docs/dev-database-integrations-adbc), and work in a schema called `docs_sql_fn_numeric_sign`. Set `QE_ENDPOINT`, `AWS_ACCESS_KEY_ID`, `AWS_SECRET_ACCESS_KEY` and `VASTDB_BUCKET` ([SQL reference](/develop/docs/dev-database-reference-sql-index#example-connect-and-use-a-transaction)), and run the blocks in order in one Python session. Below each block is the output you should see.

This block connects, defines the `run()` and `plan()` helpers, and creates a table of five price changes: a change (`DOUBLE`), a change in quantity (`INTEGER`) and an amount (`DECIMAL`). Row 4 holds a NaN change, and the last row has no values:

```
import os
import re

import adbc_driver_manager
import adbc_driver_manager.dbapi as dbapi
import adbc_driver_vastdb

BUCKET = os.environ["VASTDB_BUCKET"]
SCHEMA = f'"{BUCKET}/docs_sql_fn_numeric_sign"'

conn = dbapi.connect(
    driver=adbc_driver_vastdb.get_driver_path(),
    db_kwargs={
        "vast.db.endpoint": os.environ["QE_ENDPOINT"],
        "vast.db.access_key": os.environ["AWS_ACCESS_KEY_ID"],
        "vast.db.secret_key": os.environ["AWS_SECRET_ACCESS_KEY"],
    },
    autocommit=True,
)

def server_message(e):
    """The server's message in a driver error, without the request ID or the echoed statement."""
    text = re.sub(r"\[req=0x[0-9a-f]+\]: ", "", str(e))
    found = (re.search(r'message: "(.*?)", request_id', text, re.S)
             or re.search(r"description: (.*)\)", text, re.S))
    message = found.group(1) if found else text.strip().splitlines()[-1]
    message = re.sub(r"^Plan query: '.*?' failed with: ", "", message, flags=re.S)
    message = re.split(r"\\n|\n", message)[0].replace('\\"', '"')
    return message.replace(BUCKET, "<bucket>")

def run(sql):
    """Run one statement. Print the rows it returns, or the error."""
    try:
        with conn.cursor() as cur:
            cur.execute(sql)
            rows = cur.fetchall() if cur.description else []
    except (adbc_driver_manager.Error, OSError) as e:
        print(f"{type(e).__name__}: {server_message(e)}")
    else:
        print(rows)

def plan(sql):
    """Print the plan without its ~N Rows lines: the table's row count, which can still be 0 just after an insert."""
    with conn.cursor() as cur:
        cur.execute("EXPLAIN " + sql)
        steps = cur.fetchall()[0][1]
    print("\n".join(line for line in steps.splitlines() if "Rows" not in line))

TABLE = f"{SCHEMA}.changes"
run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}")
run(f"CREATE TABLE IF NOT EXISTS {TABLE} (id BIGINT, delta DOUBLE, qty INTEGER, amount DECIMAL(10, 2))")
run(f"INSERT INTO {TABLE} VALUES "
    "(1, 2.5, 12, 2.45), "
    "(2, -1.25, -18, -1.35), "
    "(3, 0.0, 0, 0.00), "
    "(4, 'nan'::DOUBLE, 5, 1.00), "
    "(5, NULL, NULL, NULL)")
```

```
[]
[]
[(5,)]
```

## What it does

`sign(x)` returns `-1` when `x` is less than zero, `0` when it's zero, and `1` when it's greater than zero. The result is always a `TINYINT`, whatever the type of `x`: `sign(-2.45)` is the `TINYINT` -1.

On `DOUBLE` and `FLOAT` values:

- `sign(&apos;inf&apos;::DOUBLE)` is `1` and `sign(&apos;-inf&apos;::DOUBLE)` is `-1`.
- A negative zero is zero: `sign(-0.0::DOUBLE)` is `0`. To tell `-0.0` from `0.0`, use [signbit](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid-signbit).
- **NaN gives `0`.** `sign(&apos;nan&apos;::DOUBLE)` is `0`, so `sign(x) = 0` doesn't mean `x` is zero. Test for NaN with [isnan](/develop/docs/dev-database-reference-sql-functions-numeric-isnan).
- The smallest values count: `sign(5e-324::DOUBLE)` is `1` and `sign(-1e-300)` is `-1`.

## NULLs and edge cases

| Input | Result |
| --- | --- |
| `x` is NULL | `NULL` |
| `sign(-0.0::DOUBLE)` | `0` |
| `sign(&apos;nan&apos;::DOUBLE)` | `0` |
| `sign(&apos;inf&apos;::DOUBLE)`, `sign(&apos;-inf&apos;::DOUBLE)` | `1`, `-1` |
| `sign(5e-324::DOUBLE)` | `1` |
| `sign(-2.45)` | `-1`, a `TINYINT` |
| `sign(0::UTINYINT)` | `0` |
| `sign(-9223372036854775808::BIGINT)` | Error: the cast comes before the minus, and 9223372036854775808 doesn't fit a `BIGINT` |
| A string, even `&apos;12&apos;` | Error: `Could not choose a best candidate function for the function call &quot;sign(STRING_LITERAL)&quot;` |
| A date, boolean, `BLOB`, list or interval | Error: `No function matches the given name and argument types` |

The same cases, as the cluster returns them. They use the table and helpers from [Set up the examples](/develop/docs/dev-database-reference-sql-functions-numeric-sign#set-up-the-examples):

```
run("SELECT sign(NULL), sign(-0.0::DOUBLE), sign('nan'::DOUBLE), sign('inf'::DOUBLE), sign('-inf'::DOUBLE)")
run("SELECT sign(5e-324::DOUBLE), sign(-2.45), typeof(sign(-2.45)), sign(0::UTINYINT)")
run("SELECT sign(-9223372036854775808::BIGINT)")
run("SELECT sign('12')")
run("SELECT sign(true)")
```

```
[(None, 0, 0, 1, -1)]
[(1, -1, 'TINYINT', 0)]
OSError: Type INT128 with value 9223372036854775808 can't be cast because the value is out of range for the destination type INT64
InternalError: Binder Error: Could not choose a best candidate function for the function call "sign(STRING_LITERAL)". In order to select one, please add explicit type casts.
InternalError: Binder Error: No function matches the given name and argument types 'sign(BOOLEAN)'. You might need to add explicit type casts.
```

## Examples

The sign of each column. Row 4's NaN change gives `0`, the same as row 3's zero:

```
run(f"SELECT id, sign(delta), sign(qty), sign(amount) FROM {TABLE} ORDER BY id LIMIT 10")
```

```
[(1, 1, 1, 1), (2, -1, -1, -1), (3, 0, 0, 0), (4, 0, 1, 1), (5, None, None, None)]
```

Label each change as up, down or flat, and tell NaN apart with `isnan()`:

```
run(f"SELECT id, CASE sign(delta) WHEN 1 THEN 'up' WHEN -1 THEN 'down' ELSE 'flat' END, isnan(delta) "
    f"FROM {TABLE} ORDER BY id LIMIT 10")
```

```
[(1, 'up', False), (2, 'down', False), (3, 'flat', False), (4, 'flat', True), (5, 'flat', None)]
```

Keep the falling prices:

```
run(f"SELECT id, delta FROM {TABLE} WHERE sign(delta) = -1 ORDER BY id LIMIT 10")
```

```
[(2, -1.25)]
```

## How it runs in VAST

The Query Engine runs on the cluster's CNodes, and a query on a table starts with a scan in VAST DataBase (`VAST_SCAN`). VAST DataBase can evaluate a comparison of a column with a constant, but not a function of a column, so `sign()` is always computed by the Query Engine:

- **In the `SELECT` list,** the scan reads the column and the Query Engine computes `sign()` for each row it returns.
- **In `WHERE`,** the scan sends the column for every row, and a `FILTER` step in the Query Engine computes `sign()` and keeps the rows that match. No rows are skipped in storage.

The plan of the `WHERE` example shows the `FILTER` step above the scan:

```
plan(f"SELECT id FROM {TABLE} WHERE sign(delta) = -1")
```

```
┌───────────────────────────┐
│         PROJECTION        │
│    ────────────────────   │
│             #1            │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│           FILTER          │
│    ────────────────────   │
│     (sign(delta) = -1)    │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│                           │
│        Projections:       │
│           delta           │
│             id            │
│                           │
└───────────────────────────┘
```

## Make it faster

- **Compare the raw column with zero.** `sign(delta) = -1` is the same as `delta &lt; 0`, and that form is pushed down to VAST DataBase, so rows that don't match never leave storage. Its plan has no `FILTER` step:

```
plan(f"SELECT id FROM {TABLE} WHERE delta < 0")
```

```
┌───────────────────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│      Projections: id      │
│                           │
└───────────────────────────┘
```

- **Use `sign()` in the `SELECT` list,** where it runs only on the rows the scan returns.

## Limitations and errors

- **NaN is reported as `0`.** Check `isnan(x)` when a `DOUBLE` or `FLOAT` column can hold NaN. See [What it does](/develop/docs/dev-database-reference-sql-functions-numeric-sign#what-it-does).
- **A cast binds more tightly than the minus sign.** `sign(-9223372036854775808::BIGINT)` casts 9223372036854775808 before the minus, and fails with `Type INT128 with value 9223372036854775808 can&apos;t be cast because the value is out of range for the destination type INT64`. Put the negative number in parentheses before the cast.
- **Strings aren't converted.** `sign(&apos;12&apos;)` fails with `Could not choose a best candidate function`. Cast the string to a number first.
- **Numbers only.** A date, a boolean, a `BLOB`, a list or an interval fails with `No function matches the given name and argument types`.
- **No `signum` or `sgn`.** Both fail with `Scalar Function with name ... does not exist!`. Use `sign`.

```
run("SELECT signum(-2)")
run("SELECT sign(-2), sign(CAST('-12' AS INTEGER))")
```

```
InternalError: Catalog Error: Scalar Function with name signum does not exist!
[(-1, -1)]
```

## Similar functions

| Function | Returns | Result for `-5` | Result for `-0.0::DOUBLE` |
| --- | --- | --- | --- |
| `sign(x)` | `-1`, `0` or `1`, as a `TINYINT` | `-1` | `0` |
| [signbit](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid-signbit) | whether the sign bit is set, as a `BOOLEAN` | `true` | `true` |
| [abs](/develop/docs/dev-database-reference-sql-functions-numeric-abs) | the value without its sign | `5` | `0.0` |
| [isnan](/develop/docs/dev-database-reference-sql-functions-numeric-isnan) | whether a float is NaN | `false` | `false` |

```
run("SELECT sign(-5), signbit(-5), abs(-5), sign(-0.0::DOUBLE), signbit(-0.0::DOUBLE), abs(-0.0::DOUBLE)")
run("SELECT isnan(-5), isnan(-0.0::DOUBLE), sign('nan'::DOUBLE), isnan('nan'::DOUBLE)")
```

```
[(-1, True, 5, 0, True, 0.0)]
[(False, False, 0, True)]
```

Clean up:

```
run(f"DROP TABLE IF EXISTS {TABLE}")
run(f"DROP SCHEMA IF EXISTS {SCHEMA}")
conn.close()
```

```
[]
[]
```

## See also

- [Numeric and math functions](/develop/docs/dev-database-reference-sql-functions-numeric): all the numeric functions.
- [abs](/develop/docs/dev-database-reference-sql-functions-numeric-abs), [signbit](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid-signbit) and [isnan](/develop/docs/dev-database-reference-sql-functions-numeric-isnan).
- [Where filters run](/develop/docs/dev-database-reference-sql-select#where-filters-run) and [pushdowns](/develop/docs/dev-database-reference-pushdowns).
- [EXPLAIN](/develop/docs/dev-database-reference-sql-explain): how to read a plan.