}

func (s Select) MergeClause(clause *Clause) {
	if s.Expression != nil {
		if s.Distinct {
			if expr, ok := s.Expression.(Expr); ok {
				expr.SQL = "DISTINCT " + expr.SQL
				clause.Expression = expr
				return
			}
		}

		clause.Expression = s.Expression
	} else {
		clause.Expression = s
	}
}

// CommaExpression represents a group of expressions separated by commas.
type CommaExpression struct {

	} else {
		builder.WriteByte('*')
	}
}

// MergeClause merge order by clauses
func (returning Returning) MergeClause(clause *Clause) {
	if v, ok := clause.Expression.(Returning); ok {
		returning.Columns = append(v.Columns, returning.Columns...)
	}

	clause.Expression = returning

	clause.Name = ""

	if v, ok := clause.Expression.(Limit); ok {
		if (limit.Limit == nil || *limit.Limit == 0) && v.Limit != nil {
			limit.Limit = v.Limit
		}

		if limit.Offset == 0 && v.Offset > 0 {
			limit.Offset = v.Offset
		} else if limit.Offset < 0 {
			limit.Offset = 0
		}
	}

	clause.Expression = limit

import (
	"database/sql"
	"database/sql/driver"
	"go/ast"
	"reflect"
)

// Expression expression interface
type Expression interface {
	Build(builder Builder)
}

// NegationExpressionBuilder negation expression builder
type NegationExpressionBuilder interface {
	NegationBuild(builder Builder)
}

// Expr raw expression
type Expr struct {
	SQL                string
	Vars               []interface{}

		if c, ok := stmt.Clauses["WHERE"]; ok {
			if where, ok := c.Expression.(clause.Where); ok && len(where.Exprs) >= 1 {
				for _, expr := range where.Exprs {
					if orCond, ok := expr.(clause.OrConditions); ok && len(orCond.Exprs) == 1 {
						where.Exprs = []clause.Expression{clause.And(where.Exprs...)}
						c.Expression = where
						stmt.Clauses["WHERE"] = c
						break
					}
				}
			}
		}

			}, clause.Select{
				Columns: []clause.Column{{Name: "name"}},
			}, clause.From{}},
			"SELECT `name` FROM `users`", nil,
		},
		{
			[]clause.Interface{clause.Select{
				Expression: clause.CommaExpression{
					Exprs: []clause.Expression{
						clause.NamedExpr{"?", []interface{}{clause.Column{Name: "id"}}},
						clause.NamedExpr{"?", []interface{}{clause.Column{Name: "name"}}},

		clauses := []clause.Interface{
			clause.Select{},
			clause.From{},
			clause.Where{Exprs: []clause.Expression{
				clause.Eq{Column: clause.PrimaryColumn, Value: "1"},
				clause.Gt{Column: "age", Value: 18},
				clause.Or(clause.Neq{Column: "name", Value: "jinzhu"}),
			}},
			clause.Where{Exprs: []clause.Expression{
				clause.Or(clause.Gt{Column: "score", Value: 100}, clause.Like{Column: "name", Value: "%linus%"}),
			}},

							}
						}
					} else {
						fromClause.Joins = append(fromClause.Joins, clause.Join{
							Expression: clause.NamedExpr{SQL: join.Name, Vars: join.Conds},
						})
					}
				} else {
					fromClause.Joins = append(fromClause.Joins, clause.Join{
						Expression: clause.NamedExpr{SQL: join.Name, Vars: join.Conds},
					})
				}
			}

			db.Statement.AddClause(fromClause)

				return
			}
		}

		if clause, ok := tx.Statement.Clauses["SELECT"]; ok {
			clause.Expression = nil
			tx.Statement.Clauses["SELECT"] = clause
		}
	case string:
		if strings.Count(v, "?") >= len(args) && len(args) > 0 {
			tx.Statement.AddClause(clause.Select{
				Distinct:   db.Statement.Distinct,
				Expression: clause.Expr{SQL: v, Vars: args},
			})
		} else if strings.Count(v, "@") > 0 && len(args) > 0 {

	}

	if locking.Options != "" {
		builder.WriteByte(' ')
		builder.WriteString(locking.Options)
	}
}

// MergeClause merge order by clauses
func (locking Locking) MergeClause(clause *Clause) {
	clause.Expression = locking