feature model fix (#296)

* add raw stirng quote for sql field

* remove unused code

tools/goctl/model/sql/model/ddlmodel.go

@@ -1,34 +0,0 @@
-package model
-
-import (
-	"github.com/tal-tech/go-zero/core/stores/sqlx"
-)
-
-type (
-	DDLModel struct {
-		conn sqlx.SqlConn
-	}
-	DDL struct {
-		Table string `db:"Table"`
-		DDL   string `db:"Create Table"`
-	}
-)
-
-func NewDDLModel(conn sqlx.SqlConn) *DDLModel {
-	return &DDLModel{conn: conn}
-}
-
-func (m *DDLModel) ShowDDL(table ...string) ([]string, error) {
-	var ddl []string
-	for _, t := range table {
-		query := `show create table ` + t
-		var resp DDL
-		err := m.conn.QueryRow(&resp, query)
-		if err != nil {
-			return nil, err
-		}
-
-		ddl = append(ddl, resp.DDL)
-	}
-	return ddl, nil
-}