gorm/clause/joins.go

package clause

type JoinType string

const (
	CrossJoin JoinType = "CROSS"
	InnerJoin          = "INNER"
	LeftJoin           = "LEFT"
	RightJoin          = "RIGHT"
)

// Join join clause for from
type Join struct {
	Type  JoinType
	Table Table
	ON    Where
	Using []string
}

func (join Join) Build(builder Builder) {
	if join.Type != "" {
		builder.WriteString(string(join.Type))
		builder.WriteByte(' ')
	}

	builder.WriteString("JOIN ")
	builder.WriteQuoted(join.Table)

	if len(join.ON.Exprs) > 0 {
		builder.WriteString(" ON ")
		join.ON.Build(builder)
	} else if len(join.Using) > 0 {
		builder.WriteString(" USING (")
		for idx, c := range join.Using {
			if idx > 0 {
				builder.WriteByte(',')
			}
			builder.WriteQuoted(c)
		}
		builder.WriteByte(')')
	}
}