---
title: "decade"
slug: "dev-database-reference-sql-functions-date-time-decade"
updated: 2026-10-30T18:19:01Z
published: 2026-10-30T18:19:01Z
canonical: "docs.vastdata.com/dev-database-reference-sql-functions-date-time-decade"
---

> ## 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.

# decade

*Applies to VAST Cluster 5.5.*

*[Functions](/develop/docs/dev-database-reference-sql-functions-index) › [Date and time functions](/develop/docs/dev-database-reference-sql-functions-date-time) › Parts of a date or time.* Returns the decade of a date or timestamp: its year divided by 10, without the remainder. 2024 is in decade `202`. On an interval, it returns the decades in its years.

## Syntax

```
decade(value)
```

| Argument | Type | Description |
| --- | --- | --- |
| `value` | `DATE`, `TIMESTAMP` (also `TIMESTAMP_NS`, `TIMESTAMP_MS`, `TIMESTAMP_S`) or `INTERVAL` | The value to take the decade of. |

**Returns:** `BIGINT`.

**Same as:** `date_part('decade', value)` and `extract(decade FROM value)`; see [date_part](/develop/docs/dev-database-reference-sql-functions-date-time-date-part).

## 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_date_time_decade`. 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 events. Each has a date (`d`), a timestamp (`ts`) and a timestamp with nanoseconds (`tns`). Row 4 has no values, and row 5 is the last moment of 1969:

```
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_date_time_decade"'

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}.events"
run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}")
run(f"CREATE TABLE IF NOT EXISTS {TABLE} (id BIGINT, d DATE, ts TIMESTAMP, tns TIMESTAMP_NS)")
run(f"INSERT INTO {TABLE} VALUES "
    "(1, DATE '2026-02-28', TIMESTAMP '2026-02-28 23:15:00', CAST('2026-02-28 23:15:00' AS TIMESTAMP_NS)), "
    "(2, DATE '2000-12-31', TIMESTAMP '2000-12-31 12:00:00', CAST('2000-12-31 12:00:00' AS TIMESTAMP_NS)), "
    "(3, DATE '2001-01-01', TIMESTAMP '2001-01-01 00:00:00', CAST('2001-01-01 00:00:00' AS TIMESTAMP_NS)), "
    "(4, NULL, NULL, NULL), "
    "(5, DATE '1969-12-31', TIMESTAMP '1969-12-31 23:59:59.999999', "
    "CAST('1969-12-31 23:59:59.999999999' AS TIMESTAMP_NS))")
```

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

## What it does

`decade` divides the calendar year by 10 and drops the remainder: `decade(DATE &apos;2024-02-29&apos;)` is `202`. A decade starts in a year ending in 0: `DATE &apos;2029-12-31&apos;` is in decade `202`, and `DATE &apos;2030-01-01&apos;` in decade `203`. Years 1 to 9 are in decade `0`. It works on every timestamp precision.

Years before year 1 count down from 0 (44 BC is year `-43`), and their decade is the year divided by 10 toward zero: 44 BC is in decade `-4`.

On an `INTERVAL`, `decade` returns the whole decades in its years: `decade(INTERVAL &apos;25 years&apos;)` is `2`, and `decade(INTERVAL &apos;-25 years&apos;)` is `-2`. An interval of less than 10 years, such as `INTERVAL &apos;1 year 2 months 3 days 04:05:06.789&apos;`, gives `0`.

## NULLs and edge cases

| Input | Result |
| --- | --- |
| A NULL value (row 4) | `NULL` |
| `DATE &apos;infinity&apos;`, `TIMESTAMP &apos;-infinity&apos;` | `NULL` |
| `DATE &apos;0001-01-01&apos;`, `DATE &apos;0005-01-01&apos;` | `0` |
| `DATE &apos;9999-12-31&apos;` | `999` |
| 44 BC: `CAST(&apos;0044-03-15 (BC)&apos; AS DATE)` | `-4` |
| `DATE &apos;2029-12-31&apos;` | `202` |
| `DATE &apos;2030-01-01&apos;` | `203` |
| `INTERVAL &apos;25 years&apos;` | `2` |
| `INTERVAL &apos;-25 years&apos;` | `-2` |
| `INTERVAL &apos;25 months 40 days 30 hours&apos;` | `0` |
| An untyped `NULL`: `decade(NULL)` | Error: `Could not choose a best candidate function for the function call &quot;decade(&quot;NULL&quot;)&quot;` |
| A `TIME` | Error: `No function matches the given name and argument types &apos;decade(TIME)&apos;` |
| A string | Error: `Could not choose a best candidate function`; cast it to `DATE` first |
| A number, boolean, `BLOB` or list | Error: `No function matches the given name and argument types`, for example `&apos;decade(INTEGER_LITERAL)&apos;` |

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-date-time-decade#set-up-the-examples):

```
run(f"SELECT id, decade(d), decade(ts) FROM {TABLE} WHERE id = 4")
run("SELECT decade(DATE 'infinity'), decade(TIMESTAMP '-infinity'), decade(DATE '0001-01-01'), "
    "decade(DATE '0005-01-01'), decade(DATE '9999-12-31'), decade(CAST('0044-03-15 (BC)' AS DATE)), "
    "decade(DATE '2029-12-31'), decade(DATE '2030-01-01')")
run("SELECT decade(INTERVAL '25 years'), decade(INTERVAL '-25 years'), "
    "decade(INTERVAL '25 months 40 days 30 hours')")
run("SELECT decade(NULL)")
run("SELECT decade(TIME '13:45:30')")
run("SELECT decade('2024-02-29')")
run("SELECT decade(123)")
```

```
[(4, None, None)]
[(None, None, 0, 0, 999, -4, 202, 203)]
[(2, -2, 0)]
InternalError: Binder Error: Could not choose a best candidate function for the function call "decade("NULL")". In order to select one, please add explicit type casts.
InternalError: Binder Error: No function matches the given name and argument types 'decade(TIME)'. You might need to add explicit type casts.
InternalError: Binder Error: Could not choose a best candidate function for the function call "decade(STRING_LITERAL)". In order to select one, please add explicit type casts.
InternalError: Binder Error: No function matches the given name and argument types 'decade(INTEGER_LITERAL)'. You might need to add explicit type casts.
```

## Examples

The decade of each event's date and timestamp, next to its year:

```
run(f"SELECT id, year(d), decade(d), decade(ts) FROM {TABLE} ORDER BY id LIMIT 10")
```

```
[(1, 2026, 202, 202), (2, 2000, 200, 200), (3, 2001, 200, 200), (4, None, None, None), (5, 1969, 196, 196)]
```

Keep only the events from the 2000s (decade 200). This works, but [Make it faster](/develop/docs/dev-database-reference-sql-functions-date-time-decade#make-it-faster) has a faster way to write it:

```
run(f"SELECT id FROM {TABLE} WHERE decade(d) = 200 ORDER BY id LIMIT 10")
```

```
[(2,), (3,)]
```

## 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 `decade()` is always computed by the Query Engine:

- **In the `SELECT` list,** the scan reads the column and the Query Engine computes `decade()` for each row it returns.
- **In `WHERE`,** the scan sends the column for every row, and a `FILTER` step in the Query Engine computes `decade()` 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 decade(d) = 200")
```

```
┌───────────────────────────┐
│         PROJECTION        │
│    ────────────────────   │
│             #1            │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│           FILTER          │
│    ────────────────────   │
│    ("decade"(d) = 200)    │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│                           │
│        Projections:       │
│             d             │
│             id            │
│                           │
└───────────────────────────┘
```

## Make it faster

- **Filter on a range of the raw column, not on `decade()`.** `d &gt;= DATE &apos;2000-01-01&apos; AND d &lt; DATE &apos;2010-01-01&apos;` returns the same rows as `decade(d) = 200`, and it's pushed down to VAST DataBase, so rows from other decades never leave storage. The plan for the range has no `FILTER` step:

```
run(f"SELECT id FROM {TABLE} WHERE d >= DATE '2000-01-01' AND d < DATE '2010-01-01' ORDER BY id LIMIT 10")
plan(f"SELECT id FROM {TABLE} WHERE d >= DATE '2000-01-01' AND d < DATE '2010-01-01'")
```

```
[(2,), (3,)]
┌───────────────────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│      Projections: id      │
│                           │
└───────────────────────────┘
```

- **Store the decade if you filter on it often** and a range doesn't fit your query. Compute it when you write the rows and keep it in its own column: `event_decade = 200` is pushed down, `decade(d) = 200` isn't.

## Limitations and errors

- **Dates and timestamps only, not `TIME`.** A time of day has no year, so `decade(TIME ...)` fails with `No function matches the given name and argument types &apos;decade(TIME)&apos;`.
- **No time-zone support.** On a `TIMESTAMP WITH TIME ZONE` value, such as `now()`, `decade` fails with an `Extension Autoloading Error`. Cast the value to `TIMESTAMP` first; see [time zones](/develop/docs/dev-database-reference-sql-functions-date-time-time-zones).
- **`extract(dec FROM ...)` doesn't parse.** The short name `dec` works in `date_part(&apos;dec&apos;, value)` but is a syntax error in `extract`. Write `extract(decade FROM value)`.
- **`TIMESTAMP_NS` just before 1970.** Row 5's `tns`, `1969-12-31 23:59:59.999999999`, is in decade `197`, not `196`. Store such values as `TIMESTAMP` if you need their decade.

```
run("SELECT extract(dec FROM DATE '2024-02-29')")
run(f"SELECT id, decade(tns), decade(ts) FROM {TABLE} ORDER BY id LIMIT 10")
```

```
InternalError: Parse query: 'SELECT extract(dec FROM DATE '2024-02-29')' failed with: Parser Error: syntax error at or near "dec"
[(1, 202, 202), (2, 200, 200), (3, 200, 200), (4, None, None), (5, 197, 196)]
```

## Similar functions

| Function | Returns | Result for `DATE &apos;2029-12-31&apos;` (`decade` gives `202`) |
| --- | --- | --- |
| [year](/develop/docs/dev-database-reference-sql-functions-date-time-year) | The calendar year | `2029` |
| [century](/develop/docs/dev-database-reference-sql-functions-date-time-century) | The century, counted from year 1 | `21` |
| [millennium](/develop/docs/dev-database-reference-sql-functions-date-time-millennium) | The millennium, counted from year 1 | `3` |
| [date_trunc](/develop/docs/dev-database-reference-sql-functions-date-time-date-trunc) with `&apos;decade&apos;` | The first day of the decade, as a `DATE` | `2020-01-01` |

```
run("SELECT decade(DATE '2029-12-31'), year(DATE '2029-12-31'), century(DATE '2029-12-31'), "
    "millennium(DATE '2029-12-31'), date_trunc('decade', DATE '2029-12-31')")
```

```
[(202, 2029, 21, 3, datetime.date(2020, 1, 1))]
```

Clean up:

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

```
[]
[]
```

## See also

- [date_part](/develop/docs/dev-database-reference-sql-functions-date-time-date-part): any part of a value, by name.
- [Date and time functions](/develop/docs/dev-database-reference-sql-functions-date-time): all the date and time functions.
- [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.