Add joins support

callbacks/query.go

@@ -1,6 +1,7 @@
 package callbacks
 
 import (
+	"fmt"
 	"reflect"
 
 	"github.com/jinzhu/gorm"
@@ -9,8 +10,76 @@ import (
 
 func Query(db *gorm.DB) {
 	if db.Statement.SQL.String() == "" {
-		db.Statement.AddClauseIfNotExists(clause.Select{})
-		db.Statement.AddClauseIfNotExists(clause.From{})
+		clauseSelect := clause.Select{}
+
+		if len(db.Statement.Selects) > 0 {
+			for _, name := range db.Statement.Selects {
+				if f := db.Statement.Schema.LookUpField(name); f != nil {
+					clauseSelect.Columns = append(clauseSelect.Columns, clause.Column{
+						Name: f.DBName,
+					})
+				}
+			}
+		}
+
+		if len(db.Statement.Joins) != 0 {
+			joins := []clause.Join{}
+
+			if len(db.Statement.Selects) == 0 {
+				for _, dbName := range db.Statement.Schema.DBNames {
+					clauseSelect.Columns = append(clauseSelect.Columns, clause.Column{
+						Name: dbName,
+					})
+				}
+			}
+
+			for name, conds := range db.Statement.Joins {
+				if relation, ok := db.Statement.Schema.Relationships.Relations[name]; ok {
+					for _, s := range relation.FieldSchema.DBNames {
+						clauseSelect.Columns = append(clauseSelect.Columns, clause.Column{
+							Table: relation.FieldSchema.Table,
+							Name:  s,
+						})
+					}
+
+					var exprs []clause.Expression
+					for _, ref := range relation.References {
+						if ref.OwnPrimaryKey {
+							exprs = append(exprs, clause.Expr{
+								SQL: fmt.Sprintf("%s.%s = %s.%s", db.Statement.Schema.Table, ref.PrimaryKey.DBName, relation.FieldSchema.Table, ref.ForeignKey.DBName),
+							})
+						} else {
+							if ref.PrimaryValue == "" {
+								exprs = append(exprs, clause.Expr{
+									SQL: fmt.Sprintf("%s.%s = %s.%s", db.Statement.Schema.Table, ref.ForeignKey.DBName, relation.FieldSchema.Table, ref.PrimaryKey.DBName),
+								})
+							} else {
+								exprs = append(exprs, clause.Expr{
+									SQL:  fmt.Sprintf("%s.%s = ?", relation.FieldSchema.Table, ref.PrimaryKey.DBName),
+									Vars: []interface{}{ref.PrimaryValue},
+								})
+							}
+						}
+					}
+
+					joins = append(joins, clause.Join{
+						Type:  clause.LeftJoin,
+						Table: clause.Table{Name: relation.FieldSchema.Table},
+						ON:    clause.Where{Exprs: exprs},
+					})
+				} else {
+					joins = append(joins, clause.Join{
+						Expression: clause.Expr{SQL: name, Vars: conds},
+					})
+				}
+			}
+
+			db.Statement.AddClause(clause.From{Joins: joins})
+		} else {
+			db.Statement.AddClauseIfNotExists(clause.From{})
+		}
+
+		db.Statement.AddClauseIfNotExists(clauseSelect)
 		db.Statement.Build("SELECT", "FROM", "WHERE", "GROUP BY", "ORDER BY", "LIMIT", "FOR")
 	}
 

chainable_api.go

@@ -134,6 +134,10 @@ func (db *DB) Or(query interface{}, args ...interface{}) (tx *DB) {
 //     db.Joins("JOIN emails ON emails.user_id = users.id AND emails.email = ?", "jinzhu@example.org").Find(&user)
 func (db *DB) Joins(query string, args ...interface{}) (tx *DB) {
 	tx = db.getInstance()
+	if tx.Statement.Joins == nil {
+		tx.Statement.Joins = map[string][]interface{}{}
+	}
+	tx.Statement.Joins[query] = args
 	return
 }
 
@@ -211,8 +215,12 @@ func (db *DB) Scopes(funcs ...func(*DB) *DB) *DB {
 
 // Preload preload associations with given conditions
 //    db.Preload("Orders", "state NOT IN (?)", "cancelled").Find(&users)
-func (db *DB) Preload(column string, conditions ...interface{}) (tx *DB) {
+func (db *DB) Preload(query string, args ...interface{}) (tx *DB) {
 	tx = db.getInstance()
+	if tx.Statement.Preloads == nil {
+		tx.Statement.Preloads = map[string][]interface{}{}
+	}
+	tx.Statement.Preloads[query] = args
 	return
 }
 

clause/joins.go

@@ -11,32 +11,37 @@ const (
 
 // Join join clause for from
 type Join struct {
-	Type  JoinType
-	Table Table
-	ON    Where
-	Using []string
+	Type       JoinType
+	Table      Table
+	ON         Where
+	Using      []string
+	Expression Expression
 }
 
 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)
+	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(')')
 		}
-		builder.WriteByte(')')
 	}
 }

statement.go

@@ -24,6 +24,8 @@ type Statement struct {
 	Clauses              map[string]clause.Clause
 	Selects              []string // selected columns
 	Omits                []string // omit columns
+	Joins                map[string][]interface{}
+	Preloads             map[string][]interface{}
 	Settings             sync.Map
 	ConnPool             ConnPool
 	Schema               *schema.Schema
@@ -265,6 +267,14 @@ func (stmt *Statement) reinit() {
 		delete(stmt.Clauses, k)
 	}
 
+	for k := range stmt.Joins {
+		delete(stmt.Joins, k)
+	}
+
+	for k := range stmt.Preloads {
+		delete(stmt.Preloads, k)
+	}
+
 	stmt.Settings.Range(func(k, _ interface{}) bool {
 		stmt.Settings.Delete(k)
 		return true