Source File
	joins.go

Belonging Package
	gorm.io/gorm/clause

package clause

import "gorm.io/gorm/utils"

type JoinType string

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

type JoinTarget struct {
	Type        JoinType
	Association string
	Subquery    Expression
	Table       string
}

func Has(name string) JoinTarget {
	return JoinTarget{Type: InnerJoin, Association: name}
}

func (jt JoinType) Association(name string) JoinTarget {
	return JoinTarget{Type: jt, Association: name}
}

func (jt JoinType) AssociationFrom(name string, subquery Expression) JoinTarget {
	return JoinTarget{Type: jt, Association: name, Subquery: subquery}
}

func (jt JoinTarget) As(name string) JoinTarget {
	jt.Table = name
	return jt
}

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

func JoinTable(names ...string) Table {
	return Table{
		Name: utils.JoinNestedRelationNames(names),
	}
}

func (join Join) Build(builder Builder) {
	if join.Expression != nil {
		join.Expression.Build(builder)
	} else {
		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(')')
		}
	}
}

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