使用Oracle分页

k3bvogb1  于 2022-12-11  发布在  Oracle
关注(0)|答案(7)|浏览(168)

I am not as familiar with Oracle as I would like to be. I have some 250k records, and I want to display them 100 per page. Currently I have one stored procedure which retrieves all quarter of a million records to a dataset using a data adapter, and dataset, and the dataadapter.Fill(dataset) method on the results from the stored proc. If I have "Page Number" and "Number of records per page" as integer values I can pass as parameters, what would be the best way to get back just that particular section. Say, if I pass 10 as a page number, and 120 as number of pages, from the select statement it would give me the 1880th through 1200th, or something like that, my math in my head might be off.
I'm doing this in .NET with C#, thought that's not important, if I can get it right on the sql side, then I should be cool.
Update: I was able to use Brian's suggestion, and it is working great. I'd like to work on some optimization, but the pages are coming up in 4 to 5 seconds rather than a minute, and my paging control was able to integrate in very well with my new stored procs.

gzszwxb4

gzszwxb41#

应该可以这样做:From Frans Bouma's Blog

SELECT * FROM
(
    SELECT a.*, rownum r__
    FROM
    (
        SELECT * FROM ORDERS WHERE CustomerID LIKE 'A%'
        ORDER BY OrderDate DESC, ShippingDate DESC
    ) a
    WHERE rownum < ((pageNumber * pageSize) + 1 )
)
WHERE r__ >= (((pageNumber-1) * pageSize) + 1)
kxxlusnw

kxxlusnw2#

Ask Tom和非常非常有用的分析函数。
以下是该页摘录:

select * from (
    select /*+ first_rows(25) */
     object_id,object_name,
     row_number() over
    (order by object_id) rn
    from all_objects
)
where rn between :n and :m
order by rn;
watbbzwu

watbbzwu3#

In the interest of completeness, for people looking for a more modern solution, in Oracle 12c there are some new features including better paging and top handling.

Paging

The paging looks like this:

SELECT *
FROM user
ORDER BY first_name
OFFSET 5 ROWS FETCH NEXT 10 ROWS ONLY;

Top N Records

Getting the top records looks like this:

SELECT *
FROM user
ORDER BY first_name
FETCH FIRST 5 ROWS ONLY

Notice how both the above query examples have ORDER BY clauses. The new commands respect these and are run on the sorted data.
I couldn't find a good Oracle reference page for FETCH or OFFSET but this page has a great overview of these new features.

Performance

As @wweicker points out in the comments below, performance is an issue with the new syntax in 12c. I didn't have a copy of 18c to test if Oracle has since improved it.
Interestingly enough, my actual results were returned slightly quicker the first time I ran the queries on my table (113 million+ rows) for the new method:

  • New method: 0.013 seconds.
  • Old method: 0.107 seconds.

However, as @wweicker mentioned, the explain plan looks much worse for the new method:

  • New method cost: 300,110
  • Old method cost: 30

The new syntax caused a full scan of the index on my column, which was the entire cost. Chances are, things get much worse when limiting on unindexed data.
Let's have a look when including a single unindexed column on the previous dataset:

  • New method time/cost: 189.55 seconds/998,908
  • Old method time/cost: 1.973 seconds/256

Summary: use with caution until Oracle improves this handling. If you have an index to work with, perhaps you can get away with using the new method.
Hopefully I'll have a copy of 18c to play with soon and can update

gopyfrb3

gopyfrb34#

只是想总结一下答案和评论。分页的方法有很多。
在oracle 12 c之前,没有OFFSET/FETCH功能,所以看一下@jasonk建议的whitepaper。这是我找到的关于不同方法的最完整的文章,详细解释了优点和缺点。在这里复制粘贴它们会花费大量的时间,所以我不做了。
还有一篇来自jooq创建者的好文章,解释了oracle和其他数据库分页的一些常见注意事项。
好消息是,自Oracle 12 c以来,我们有了新的OFFSET/FETCH功能。OracleMagazine 12c new features。请参阅“Top-N查询和分页”
可以通过发出以下语句来检查oracle版本

SELECT * FROM V$VERSION
4bbkushb

4bbkushb5#

请尝试以下操作:

SELECT *
FROM
  (SELECT FIELDA,
    FIELDB,
    FIELDC,
    ROW_NUMBER() OVER (ORDER BY FIELDC) R
  FROM TABLE_NAME
  WHERE FIELDA = 10
  )
WHERE R >= 10
AND R   <= 15;

通过tecnicume(http://mbfu.it/r/ta)

dfuffjeb

dfuffjeb6#

In my project I used Oracle 12c and java. The paging code looks like this:

public public List<Map<String, Object>> getAllProductOfferWithPagination(int pageNo, int pageElementSize, Long productOfferId, String productOfferName) {
    try {

        if(pageNo==1){
            //do nothing
        } else{
            pageNo=(pageNo-1)*pageElementSize+1;
        }
        System.out.println("algo pageNo: " + pageNo +"  pageElementSize: "+ pageElementSize+"  productOfferId: "+ productOfferId+"  productOfferName: "+ productOfferName);

        String sql = "SELECT * FROM ( SELECT * FROM product_offer po WHERE po.deleted=0 AND (po.product_offer_id=? OR po.product_offer_name LIKE ? )" +
             " ORDER BY po.PRODUCT_OFFER_ID asc) foo OFFSET ? ROWS FETCH NEXT ? ROWS ONLY ";

       return jdbcTemplate.queryForList(sql,new Object[] {productOfferId,"%"+productOfferName+"%",pageNo-1, pageElementSize});

    } catch (Exception e) {
        System.out.println(e);
        e.printStackTrace();
        return null;
    }
lzfw57am

lzfw57am7#

In SomeServiceClass 
    using npoco
    
    public async Task<List<SomeModel>> SomeServiceMethod(int pageIndex, int pageSize)
    
                    int lowerLimit;
                    int higherLimit;
    //This would help limit the result to 300 max. If the PageSize is stated as 290
    //we get the 1st to 289th result. If page size is 1845.
    //It returns 1845 - 299 = 1546. 1546th element to 1844th element
    
                    if((pageSize) < 300)
                    {
                        lowerLimit = 1;
                        higherLimit = pageSize;
                    }
                    else
                    {
                        int subtract = 300 - 1;
                        lowerLimit = pageSize - subtract;
                        higherLimit = pageSize;
                    }
    
    //Using Brian Schmitt script

    List<SomeModel> someVariableName = db.Query<SomeModel>(SELECT * FROM
    (
        SELECT a.*, rownum r__
        FROM
        (
            SELECT * FROM ORDERS WHERE CustomerID LIKE 'A%'
            ORDER BY OrderDate DESC, ShippingDate DESC
        ) a
        WHERE rownum < (@0)
    )
    WHERE r__ >= (@1), higherlimit, lowerlimit).ToList();
    
    
    
    In SomeControllerClass

    [HttpGet]
    [Route("SomeControllerMethod")]
    public async Task<SomeResponseModel> SomeControllerMethod(int pageIndex, int pageSize)
    
    SomeServiceClass ssc = new SomeServiceClass();
    SomeResponseModel srm = new SomeResponseModel();
    
    List<SomeModel> resp = await ssc.SomeServiceMethod(pageIndex, pageSize);
    
    //Paging on API level, solution is from CSharpCorner. This would return a //max of 20 elements per page. 
    //So if you have a result of 300. It would be divided into 15 pages.
    //20 results per page. 

                    int totalRecords = resp.Count();
    
    
                    const int maxPageSize = 20;
                    pageSize = (pageSize > maxPageSize) ? maxPageSize : pageSize;
                    int pageNum = pageIndex;
                    int recordToTake = totalRecords - (pageNum - 1) * pageSize;
                    int CurrentPage = pageNum;
                    int TotalPages = (int)Math.Ceiling(totalRecords / (double)pageSize);
                    var previousPage = CurrentPage > 1 ? "Yes" : "No";
                    var nextPage = CurrentPage < TotalPages ? "Yes" : "No";
                    List<SomeModel> filteredResult = resp.Skip((CurrentPage - 1) * pageSize).Take(pageSize).ToList();
    
    
                    
                    srm.records = totalRecords;
                    srm.previousPage = previousPage;
                    srm.currentPage = $"Page: {CurrentPage} / {TotalPages}";
                    srm.nextPage = nextPage;
                    srm.totalPages = TotalPages;
                    srm.someIEnumerableProperty = filteredResult;
    
    return srm;

//How to use endpoint
//http://localhost:somePort/someControllerClass/SomeControllerMethod?pageIndex={pageIndex}&pageSize={pageSize}

//pageIndex will take value 1 to 15 since we have a max of 300 and 20 results per page.
//pageSize will be used to determine our higherlimit

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