# VECTOR\_SUBVECTOR

Derives a vector expression from another vector expression.

It is a scalar function.

## Syntax

```sql
VECTOR_SUBVECTOR(vector_expression, start_position, length)
```

## Arguments

* `vector_expression`: An expression that evaluates to a vector. The vector must be encoded as a blob containing packed single-precision or double-precision floating-point numbers in little-endian byte order.
* `start_position`: A 0-indexed number to determine where to start count. A positive index counts from the beginning of the vector. A negative index counts from the end of the vector.
* length: Length of required subvector

## Return Type

A blob containing packed single-precision floating-point numbers in little-endian byte order.

## Remarks

If the input is `NULL`, `NULL` will be returned.

You can specify the data type of the vector elements in which this operation is performed on the vector by adding a suffix to the function. Omitting the suffix from the function is equivalent to suffixing it with `_F32`. All operations are done using the specified data type. The following table lists the suffixes and their data type.

| Suffix | Data Type                                           |
| ------ | --------------------------------------------------- |
| `_I8`  | 8-bit signed integer                                |
| `_I16` | 16-bit signed integer                               |
| `_I32` | 32-bit signed integer                               |
| `_I64` | 64-bit signed integer                               |
| `_F32` | 32-bit floating-point number (IEEE standard format) |
| `_F64` | 64-bit floating-point number (IEEE standard format) |

## Examples

```sql
CREATE TABLE vsv_t (x BLOB);
INSERT INTO vsv_t VALUES (JSON_ARRAY_PACK('[1,2,3,4,5]'));
```

```sql
SELECT JSON_ARRAY_UNPACK (VECTOR_SUBVECTOR(x,2,2)) AS x from vsv_t;

```

```output

+-------+
| x     |
+-------+
| [3,4] |
+-------+

```

```sql
SELECT JSON_ARRAY_UNPACK (VECTOR_SUBVECTOR(x,-2,2)) AS x from vsv_t;

```

```output

+-------+
| x     |
+-------+
| [4,5] |
+-------+
```

## How to Use the Vector Data Type

Currently, `VECTOR_SUBVECTOR`  is not supported with the vector data type. A workaround is provided until support for the vector data type is implemented.

Using `VECTOR_SUBVECTOR` with the vector data type will result in an error.

```sql
SELECT vector_subvector(position, 1, 2) FROM vector_exps;


```

```output

ERROR 1940 ER_VECTOR_FUNCTION_ERROR: Error with a vector function: 
Function `vector_subvector` is not supported with VECTOR datatype.
```

There is a way to use  `VECTOR_SUBVECTOR` with a vector data type. First cast to a blob data type and then cast back to a vector data type. The example below shows how to do this:

## Example

Set the position column to use vectors and the vector data type:

```sql
SET @pos = '[1,2,3,4]':>vector(4);
```

Cast to a blob data type:

```sql
SELECT vector_subvector(@pos:>blob, 1,2);


```

```output

+------------------------------------+
| vector_subvector(@pos:>blob, 1, 2) |
+------------------------------------+
|    @@@                             |
+------------------------------------+
```

Cast to a vector data type:

```sql
SELECT vector_subvector(@pos:>blob, 1, 2):>vector(2);


```

```output

+-----------------------------------------------+
| vector_subvector(@pos:>blob, 1, 2):>vector(2) |
+-----------------------------------------------+
| [2,3]                                         |
+-----------------------------------------------+
```

***

Modified at: January 26, 2024

Source: [/db/v9.1/reference/sql-reference/vector-functions/vector-subvector/](https://docs.singlestore.com/db/v9.1/reference/sql-reference/vector-functions/vector-subvector/)

(An index of the documentation is available at /llms.txt)