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Extend D1 docs with clarifications for one-way type conversions #22093

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May 1, 2025
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Extend D1 docs with clarifications for one-way type conversions #22093

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Extend D1 docs with clarifications for one-way type conversions
lambrospetrou Apr 30, 2025
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Oxyjun May 1, 2025
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46 changes: 32 additions & 14 deletions src/content/docs/d1/worker-api/index.mdx
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Expand Up @@ -40,26 +40,44 @@ const result = await env.MY_DB.prepare(

## Type conversion

D1 automatically converts supported JavaScript (including TypeScript) types passed as parameters via the Workers Binding API to their associated D1 types. The type conversion is as follows:

| JavaScript | D1 |
| -------------------- | ---------------------------------------------------------------------------- |
| null | `NULL` |
| Number | `REAL` |
| Number <sup>1</sup> | `INTEGER` |
| String | `TEXT` |
| Boolean <sup>2</sup> | `INTEGER` |
| ArrayBuffer | `BLOB` |
| undefined | Not supported. Queries with `undefined` values will return a `D1_TYPE_ERROR` |

<sup>1</sup> D1 supports 64-bit signed `INTEGER` values internally, however
D1 automatically converts supported JavaScript (including TypeScript) types passed as parameters via the Workers Binding API to their associated D1 types <sup>1</sup>.
This conversion is permanent and one-way only. This means that when reading the written values back in your code, you will get the converted values rather than the originally inserted values.

:::note
We recommend using [STRICT tables](https://www.sqlite.org/stricttables.html) in your SQL schema to avoid issues with mismatched types between values that are actually stored in your database compared to values defined by your schema.
:::

The type conversion during writes is as follows:

| JavaScript (write) | D1 | JavaScript (read) |
| -------------------- | --------------------------- | ------------------ |
| null | `NULL` | null |
| Number | `REAL` | Number |
| Number <sup>2</sup> | `INTEGER` | Number |
| String | `TEXT` | String |
| Boolean <sup>3</sup> | `INTEGER` | Number (`0`,`1`) |
| ArrayBuffer | `BLOB` | Array <sup>4</sup> |
| ArrayBuffer View | `BLOB` | Array <sup>4</sup> |
| undefined | Not supported. <sup>5</sup> | - |

<sup>1</sup> D1 types correspond to the underlying [SQLite
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@Oxyjun How can we make the footnotes to show on hover? I assume there is some component we can migrate too?

Feel free to checkout and edit this PR directly, BTW.

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I'll tackle the footnotes in a separate PR across all the pages. For reference though, this is how the hover footnote works:

Text [^1]

[^1]: Footnote

https://developers.cloudflare.com/style-guide/components/footnotes/

types](https://www.sqlite.org/datatype3.html).

<sup>2</sup> D1 supports 64-bit signed `INTEGER` values internally, however
[BigInts](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt)
are not currently supported in the API yet. JavaScript integers are safe up to
[`Number.MAX_SAFE_INTEGER`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER).

<sup>2</sup> Booleans will be cast to an `INTEGER` type where `1` is `TRUE` and
<sup>3</sup> Booleans will be cast to an `INTEGER` type where `1` is `TRUE` and
`0` is `FALSE`.

<sup>4</sup> `ArrayBuffer` and [`ArrayBuffer`
views](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer/isView)
are converted using
[`Array.from`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/from).

<sup>5</sup> Queries with `undefined` values will return a `D1_TYPE_ERROR`.

## API playground

The D1 Worker Binding API playground is an `index.js` file where you can test each of the documented Worker Binding APIs for D1. The file builds from the end-state of the [Get started](/d1/get-started/#write-queries-within-your-worker) code.
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