# form

## Description

One application/x-www-form-urlencoded record: key=value\&key=value. Percent escapes and plus-as-space decoding apply to values. file() can infer String columns when no explicit schema is supplied.

Only values are URL-decoded; keys retain their literal spelling, including dots
and percent sequences. Repeated keys are rejected, ignoring ASCII case. A final
LF or CRLF may terminate the record.

Input only. Select it with `FORMAT form`. Names ignore ASCII case; use the snake_case name shown here.

The input represents one row of key/value pairs, rather than a stream of several records. Values decode percent escapes and plus signs; keys keep their literal spelling. Repeated keys are rejected without regard to ASCII case.

A file() source can infer String fields from nonempty input. Supply an explicit schema to choose native conversions or to describe an empty form. The format has no output encoder.

```text
INSERT INTO table [(columns)] [SETTINGS ...] FORMAT form
<data>
```

## Example usage

```sql
SELECT name,is_input,is_output FROM system.formats WHERE name='form' FORMAT csv;
```

```text
"form",1,0
```

Example input: `id=7&name=Ada+Lovelace`.

## Format settings

Use a statement `SETTINGS` clause; these options are not persisted by `SET`.

| Setting                 | Type     | Default | Meaning                                                                                  |
| ----------------------- | -------- | ------- | ---------------------------------------------------------------------------------------- |
| `ignore_unknown_fields` | `Bool`   | `0`     | Skip input keys and header names that match no target column instead of failing.         |
| `snappy_mode`           | `String` | `basic` | Read Snappy client files as basic (Hadoop blocks) or framed (standard streaming format). |

## Load rows

Run the INSERT request separately; its remaining bytes are input data.

```sql
CREATE TABLE form_input(id UInt8,name String);
```

```text
OK
```

```sql
INSERT INTO form_input FORMAT form
id=7&name=Ada+Lovelace
```

```text
OK
```

```sql
SELECT * FROM form_input FORMAT csv;
```

```text
7,"Ada Lovelace"
```