Question

我有这样的表：

release    release_id
a          1
b          2
c          3
d          4
a          5
f          6
a          7
b          8

如何更新以使同一版本具有相同的ID？我知道更新命令。但我不知道该怎么做..

Answer 1

    @RequestMapping(value = "/user/search", method = RequestMethod.POST,produces = "text/plain;charset=UTF-8")
    public String listUsersSort(
            @RequestParam(value="weight") int weight,
            @RequestParam(value="gender") String gender,
            @RequestParam(value="place") String place,
            @RequestParam(value="age") int age,
            Model model, Principal principal)
    {

        System.out.println("int");
        if(weight<40 && gender.equals("") && place.equals("") && age<19)
        {
            model.addAttribute("users", new Users());
model.addAttribute("noparams", "Задайте параметры поиска");
return "searchingUser";
        }

        else{
    model.addAttribute("users", new Users());
        model.addAttribute("listUsersSort", usersService.listUsersSort(weight, gender, place, age, principal.getName()));
        model.addAttribute("allUserMess", this.dialogService.allNewMessForUser(principal.getName()));
        model.addAttribute("countOfFeedbacks", this.feedbackService.checkUnreadFedbacks().size());
        model.addAttribute("countOfNewUsers", this.usersService.countOfNewUsers());
        return "searchingUser";
        }}

Answer 2

另一种方法是从包含每个release及其最小release_id的派生表进行更新。如果每个版本重复多次，派生表可能比子查询更快，因为每个版本的min release_id只检索一次。

merge into mytable t1
using 
(
    select release, min(release_id) release_id
    from mytable
    group by release
) t2 on (t1.release = t2.release)
when matched then update 
    set t1.release_id = t2.release_id

此查询可以利用(release,release_id)

上的综合索引

如何将id更改为相同

2 个答案: