## SQL Builder

SQL Builder files are Go files, containing types necessary to write type safe SQL queries in Go. They are 
autogenerated from database tables and enums. 

### Table SQL Builder files

Following rules are applied to generate table SQL Builder files:

- for every table there is one Go SQL Builder file generated. File name is in snake case of the table name. 
- every file contains one type - struct with nested jet.Table. Type name is a camel case of table name.
- for every column of table there is a field column in SQL Builder table type. Field name is camel case of column name. 
See below table for type mapping.
- `AllColumns` is used as shorthand notation for list of all columns.
- `MutableColumns` are all columns minus primary key columns _(Useful in INSERT or UPDATE statements)_.

##### Mappings of database types to sql builder column types:

| Database type(postgres)                         | Sql builder column type                                            |
| ----------------------------------------------- | -------------------------------------------------- |
| boolean                                         |  ColumnBool                                        |
| smallint, integer, bigint                       |  ColumnInteger                                     |
| real, numeric, decimal, double precision        |  ColumnFloat                                       |
| date                                            |  ColumnDate                                        |
| timestamp without time zone                     |  ColumnTimestamp                                   |
| timestamp with time zone                        |  ColumnTimestampz                                  |
| time without time zone                          |  ColumnTime                                        |
| time with time zone                             |  ColumnTimez                                       |
| enums, text, character, character varying       |                                                    |
| bytea, uuid                                     |                                                    |
| and all remaining types                         |  ColumnString                                      |

### Example

Sql table `address`:
```
CREATE TABLE dvds.address
(
    address_id serial NOT NULL DEFAULT,
    address character varying(50) NOT NULL,
    address2 character varying(50),
    district character varying(20) NOT NULL,
    city_id smallint NOT NULL,
    postal_code character varying(10),
    phone character varying(20) NOT NULL,
    last_update timestamp without time zone NOT NULL DEFAULT now(),
    CONSTRAINT address_pkey PRIMARY KEY (address_id)
)
```

Part of the table sql builder file for table `address`. 

```
package table

import (
	"github.com/go-jet/jet"
)

var Address = newAddressTable()

type AddressTable struct {
	jet.Table

	//Columns
	AddressID  jet.ColumnInteger
	Address    jet.ColumnString
	Address2   jet.ColumnString
	District   jet.ColumnString
	CityID     jet.ColumnInteger
	PostalCode jet.ColumnString
	Phone      jet.ColumnString
	LastUpdate jet.ColumnTimestamp

	AllColumns     jet.ColumnList
	MutableColumns jet.ColumnList
}
```

### Enum SQL Builder files

Following rules are applied to generate enum SQL Builder files:

- for every enum there is one Go SQL Builder file generated. File name is in snake case of the enum name. 
- every file contains one type. Type name is a camel case of enum name.
- for every enum value there is a field in SQL Builder enum struct. Field name is camel case of enum value. Type is
jet.StringExpression, meaning it can be used by string expressions methods.

#### Example

Enum `mpaa_rating`:
```
CREATE TYPE dvds.mpaa_rating AS ENUM
    ('G', 'PG', 'PG-13', 'R', 'NC-17');
```

Enum SQL Builder file for `mpaa_rating`:
```
package enum

import "github.com/go-jet/jet"

var MpaaRating = &struct {
	G    jet.StringExpression
	PG   jet.StringExpression
	PG13 jet.StringExpression
	R    jet.StringExpression
	NC17 jet.StringExpression
}{
	G:    jet.NewEnumValue("G"),
	PG:   jet.NewEnumValue("PG"),
	PG13: jet.NewEnumValue("PG-13"),
	R:    jet.NewEnumValue("R"),
	NC17: jet.NewEnumValue("NC-17"),
}
```