golang通过mysql语句实现分页查询

1.前端接口调用

2.register访问入口

 //查询一个用户下所有的subnet
ws.Route(ws.GET("/subnets").
To(sc.ListSubnet).
Doc("List subnets authorized to the login user.").
Param(ws.QueryParameter(query.ParameterPage, "page").Required(false).DataFormat("page=%d").DefaultValue("page=1")).
Param(ws.QueryParameter(query.ParameterLimit, "limit").Required(false)).
Returns(http.StatusOK, api.StatusOK, api.ListResult{}))  

3.解析参数

 //查询某个用户下所有的subnet信息
func (v *SubController) ListSubnet(request *restful.Request, response *restful.Response) {
username := request.Attribute(filters.UserName).(string)
 
subnetService := &service.SubnetService{}
query := query.ParseQueryParameter(request)
result, err := subnetService.ListSubnet(query, v.Db, username)
if err != nil {
api.HandleError(response, request, err)
return
}
response.WriteEntity(result)
}  

4.service实现

 //查询一个用户所有的subnet信息
func (ss *SubnetService) ListSubnet(query *query.Query, db *sql.DB, userName string) (*api.ListResult, error) {
sm := mapper.NewSubnetMapper(db)
sb, err := sm.SearchAllByUserName(query, userName)
return sb, err
}  

5.mapper实现

 //查询用户下的所以信息
func (s *SubnetMapper) SearchAllByUserName(query *query.Query, userName string) (*api.ListResult, error) {
 
totalRow, err := s.Db.Query("SELECT COUNT(*) from t_subnet ,t_vpc where t_vpc.id = t_subnet.vpcid and username = ?", userName)
if err != nil {
klog.Error("query orders count error", err)
return nil, err
}
total := 0
for totalRow.Next() {
err := totalRow.Scan(
&total,
)
if err != nil {
klog.Error("query orders count error", err)
continue
}
}
totalRow.Close()
 
rows, err := s.Db.Query(SearchAllByUserNameSql, userName, query.Pagination.Limit, query.Pagination.Offset)
defer func() {
if rows != nil {
rows.Close()
}
}()
if err != nil {
klog.Error("query subnet error", err)
return nil, err
}
items := make([]interface{}, 0)
for rows.Next() {
ss := new(vpc.SubnetItem)
err = rows.Scan(&ss.VpcName, &ss.VpcNetwork, &ss.SubnetName, &ss.SubnetNetwork, &ss.CreateTime)
items = append(items, *ss)
}
return &api.ListResult{
TotalItems: total,
Items: items,
}, nil
}  

可以看到第一步查出了所有count数目：

查询语句加上参数。控制查到的页数。

返回的是总数量跟当前查询页。

特殊情况用不到数据库分页的，就需要用到内存分页了.