# Datatypes

`sqlc` attempts to make reasonable default choices when mapping internal
database types to Go types. Choices for more complex types are described below.

If you're unsatisfied with the default, you can override any type using the
[overrides list](config.html#type-overriding) in your `sqlc` config file.

## Arrays

PostgreSQL [arrays](https://www.postgresql.org/docs/current/arrays.html) are
materialized as Go slices.

```sql
CREATE TABLE places (
  name text   not null,
  tags text[]
);
```

```go
package db

type Place struct {
	Name string
	Tags []string
}
```

## Dates and Time

All PostgreSQL time and date types are returned as `time.Time` structs. For
null time or date values, the `NullTime` type from `database/sql` is used.
The `pgx/v5` sql package uses the appropriate pgx types.

```sql
CREATE TABLE authors (
  id         SERIAL    PRIMARY KEY,
  created_at timestamp NOT NULL DEFAULT NOW(),
  updated_at timestamp
);
```

```go
package db

import (
	"database/sql"
	"time"
)

type Author struct {
	ID        int
	CreatedAt time.Time
	UpdatedAt sql.NullTime
}
```

## Enums

PostgreSQL [enums](https://www.postgresql.org/docs/current/arrays.html) are
mapped to an aliased string type.

```sql
CREATE TYPE status AS ENUM (
  'open',
  'closed'
);

CREATE TABLE stores (
  name   text    PRIMARY KEY,
  status status  NOT NULL
);
```

```go
package db

type Status string

const (
	StatusOpen   Status = "open"
	StatusClosed Status = "closed"
)

type Store struct {
	Name   string
	Status Status
}
```

## Null

For structs, null values are represented using the appropriate type from the
`database/sql` or `pgx` package.

```sql
CREATE TABLE authors (
  id   SERIAL PRIMARY KEY,
  name text   NOT NULL,
  bio  text
);
```

```go
package db

import (
	"database/sql"
)

type Author struct {
	ID   int
	Name string
	Bio  sql.NullString
}
```

## UUIDs

The Go standard library does not come with a `uuid` package. For UUID support,
sqlc uses the excellent `github.com/google/uuid` package. The pgx/v5 sql package uses `pgtype.UUID`.

```sql
CREATE TABLE records (
  id   uuid PRIMARY KEY
);
```

```go
package db

import (
	"github.com/google/uuid"
)

type Author struct {
	ID uuid.UUID
}
```

For MySQL, there is no native `uuid` data type. When using `UUID_TO_BIN` to store a `UUID()`, the underlying field type is `BINARY(16)` which by default sqlc would interpret this to `sql.NullString`. To have sqlc automatically convert these fields to a `uuid.UUID` type, use an overide on the column storing the `uuid`.
```json
{
  "overrides": [
    {
      "column": "*.uuid",
      "go_type": "github.com/google/uuid.UUID"
    }
  ]
}
```

## JSON

By default, sqlc will generate the `[]byte`, `pgtype.JSON` or `json.RawMessage` for JSON column type.
But if you use the `pgx/v5` sql package then you can specify a some struct instead of default type.
The `pgx` implementation will marshall/unmarshall the struct automatically.

```go
package dto

type BookData struct {
	Genres    []string `json:"genres"`
	Title     string   `json:"title"`
	Published bool     `json:"published"`
}
```

```sql
CREATE TABLE books (
  data jsonb
);
```

```json
{
  "overrides": [
    {
      "column": "books.data",
      "go_type": {
        "import":"example/db",
        "package": "dto",
        "type":"BookData"
      }
    }
  ]
}
```

```go
package db

import (
	"example.com/db/dto"
)

type Book struct {
    Data *dto.BookData
}
```
