# yamltodb - YAML to Database

`yamltodb` — generate SQL statements to update a PostgreSQL database to match the schema specified in YAML files

## Synopsis

```
yamltodb [option...] dbname spec
```

## Description

**yamltodb** is a utility for generating SQL statements to update a
PostgreSQL database so that it will match the schema specified in
YAML-formatted specification file(s).

For example, given the sample output shown under {doc}`dbtoyaml`,
**yamltodb**, when run against a newly-created database, outputs the
following SQL statements:

```sql
CREATE TABLE public.film (id integer NOT NULL, title character varying(32))
ALTER TABLE public.film ADD CONSTRAINT film_pkey PRIMARY KEY (id)
```

## Positional arguments

`dbname`
:   The name of the database whose schema is to be analyzed.

`spec`
:   Path to the YAML file(s)

## Options

**yamltodb** accepts the following arguments (in addition to the
{doc}`common-options`):

`-B`, `--single-transaction`
:   Wrap the generated statements in a single transaction (BEGIN/COMMIT).

`-o <file>`, `--output <file>`
:   Send the generated SQL statements to the specified *file* name. By
    default, they are printed to standard output.

`-u`, `--update`
:   Execute the generated statements against the database mentioned in
    `dbname`. This implies the `--single-transaction` option.

## Examples

To generate SQL statements without executing it:

```
yamltodb testdb testdb.yaml
```

To write the SQL to a file without executing:

```
yamltodb -o testdb.sql testdb testdb.yaml
```

To apply changes directly:

```
yamltodb testdb testdb.yaml --update
```

To wrap the output in a single transaction:

```
yamltodb testdb testdb.yaml --single-transaction
```

To connect to a specific host and port:

```
yamltodb -H somehost -p 5433 testdb testdb.yaml --update
```