那些可以在數(shù)據(jù)庫里做的事：分頁與過濾

昵稱10504424 2014-04-10

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其實很多非業(yè)務(wù)邏輯的功能，比如分頁，數(shù)據(jù)過濾，可以在程序上面節(jié)省很多內(nèi)存和CPU時間，但往往又找不到一個比較通用有效的方法，花了點時間，終于把我想要的在數(shù)據(jù)庫中分頁和過濾的功能寫了出來，在這里分享。

第一期望：我希望輸入頁碼（pageIndex），每頁顯示的記錄數(shù)(pageSize)，然后這個存儲過程就可以給我一個當(dāng)前頁的數(shù)據(jù)集。

首先，我假設(shè)有個表叫Configuration，里面就3個字段，Id, Key, Value，就是一個簡單的數(shù)據(jù)表，定義如下：

CREATE TABLE [dbo].[Configuration]
(
    [Id] int NOT NULL IDENTITY (1,1), 
    [Key] varchar(20) NOT NULL UNIQUE,
    [Value] nvarchar(max) NULL
)

再者，一個良好的代碼書寫規(guī)范是非常必要的，該注釋的地方千萬別省，在多數(shù)情況下，代碼的可讀性是非常重要的，除非因性能因素做必須得讓步。

/*
PROCEDURE:    [dbo].[sp_r_p_configuration]
OPERATION:    READ
FEATURES:        Paginate
PURPOSE:        provide a paginated list from the configuration table
CREATOR:        Jerry Weng
CREATETIME:    2014-4-9
UPDATETIME:    2014-4-9
VERSION:        1.0
*/

CREATE PROCEDURE [dbo].[sp_r_p_configuration]
    @pageIndex int = 1,                    /*which page of the total page*/
    @pageSize int=10,                    /*how many records show in one page*/
    @recordCount int OUTPUT,        /*output: return the count of the total records in all pages*/
    @pageCount int OUTPUT            /*output: return the count of the total pages*/
AS
    declare @startRow int;                -- the row number of the first record in the page
    declare @endRow int;                -- the row number of the last record in the page
    set @startRow = (@pageIndex - 1) * @pageSize + 1;
    set @endRow= @startRow + @pageSize - 1;

    ;with tmp as 
    (select (ROW_NUMBER() over(order by Id)) as row_id, [Id], [Key], [Value] 
    from dbo.Configuration)
    select [Id], [Key], [Value] from tmp
    where row_id between @startRow and @endRow
    
    -- calculate the record count in all pages
    select @recordCount=COUNT(*) from dbo.Configuration
    -- calculate the page count
    set @pageCount = CEILING(@recordCount/CAST(@pageSize as float))

RETURN 0

這里用的ROW_NUMBER()來實現(xiàn)分頁，性能必拼SQL的方法好，WITH...AS可以省下一個表變量。最后計算總記錄數(shù)和頁數(shù)很簡單，算下就好了。

第二期望：這樣的，似乎差不多了，但是我還希望能夠有一套規(guī)則，來過濾結(jié)果集，并且還要有類似AND和OR的運算功能，而且我仍舊不希望用inline-script去實現(xiàn)，能不用盡量不要用。

為了實現(xiàn)這個期望，我需要先定義怎么傳入過濾規(guī)則，我最終決定用的是xml數(shù)據(jù)類型而不是普通字符串，因為普通字符串有長度限制（如果你說可以用text，那我只能說太奢侈，小弟用不起），定短了可能被截斷出現(xiàn)錯誤輸出，定長了，最多也就8000個字符，也浪費，我不喜歡不確定因素，然而xml不一樣，既是結(jié)構(gòu)化數(shù)據(jù)，又有索引支持，可長可短，客戶端也可直接序列化成字符串傳入，非常方便。于是剩下的是，約定一個規(guī)則，確定過濾規(guī)則的數(shù)據(jù)結(jié)構(gòu)，在這里我專門寫了一個function來將xml轉(zhuǎn)換成table已被后用。P.S. 如果想傳一個數(shù)組到存儲過程，也可以用xml類型，比字符串加分隔符更安全。

/*
FUNCTION:        [dbo].[fun_xmlfilter_parse]
OPERATION:    READ
FEATURES:        
PURPOSE:        parse a table from a xml with the specific column name
CREATOR:        Jerry Weng
CREATETIME:    2014-4-9
UPDATETIME:    2014-4-9
VERSION:        1.0
*/

CREATE FUNCTION [dbo].[fun_xmlfilter_parse]
(
    @filter xml,                    /*    The format should be:
                                        <filter>
                                            <rule 
                                                column="COLUMN_NAME"    -- the column name which the rule should be applied
                                                match="xxx"                    -- the key which the rule defines to filter and the result should match
                                                required="0|1"                    -- if 1, the result collection has to meet this rule or return nothing
                                             />
                                             <rule ....
                                        </filter>
                                    */
    @column varchar(100)
)
RETURNS @returntable TABLE 
(
    [Match] nvarchar(100),
    [Required] bit
)
AS
BEGIN
    ;with tmp as
    (
    select
            [T].[RULE].value('@column','varchar(100)') as [Column],
            [T].[RULE].value('@match','nvarchar(100)') as [Match],
            [T].[RULE].value('@required','bit') as [Required]
    from @filter.nodes('filter//rule') [T]([RULE])
    )
    INSERT @returntable
    select [Match],[Required] from tmp where [Column] = @column
        
    RETURN 
END

/*
PROCEDURE:    [dbo].[sp_r_fp_configuration]
OPERATION:    READ
FEATURES:        Paginate, Filter
PURPOSE:        provide a paginated & filterable list from the configuration table
CREATOR:        Jerry Weng
CREATETIME:    2014-4-9
UPDATETIME:    2014-4-9
VERSION:        1.0
*/

CREATE PROCEDURE [dbo].[sp_r_fp_configuration]
    @pageIndex    int = 1,                /*which page of the total page*/
    @pageSize        int=10,                /*how many records show in one page*/
    @filter            xml,                    /*filter string for the records*/
    @recordCount int OUTPUT,        /*output: return the count of the total records in all pages*/
    @pageCount    int OUTPUT            /*output: return the count of the total pages*/
AS
    if(@filter is null)
    begin
        exec dbo.sp_r_p_configuration 
                @pageIndex,
                @pageSize,
                @pageCount=@pageCount OUTPUT, 
                @recordCount=@recordCount OUTPUT
    end
    else
    begin
        
        declare @tmptbl table (row_id int, Id int, [Key] varchar(100), [Value] varchar(200))
    
        declare @startRow int;                -- the row number of the first record in the page
        declare @endRow int;                -- the row number of the last record in the page
        set @startRow = (@pageIndex - 1) * @pageSize + 1;
        set @endRow= @startRow + @pageSize - 1;

        insert into @tmptbl
            select (ROW_NUMBER() over (order by m.Id)) as row_id, m.[Id], m.[Key], m.[Value] 
            from dbo.Configuration as m
            outer apply fun_xmlfilter_parse(@filter,'key') as k
            outer apply fun_xmlfilter_parse(@filter,'value') as v
            where 
            (
                not (isnull(k.[Required],0)=0 and isnull(v.[Required],0)=0) and
                (isnull(k.[Required],0)=0 or (k.[Required] = 1 and isnull(m.[Key],'') = isnull(k.[Match],''))) and
                (isnull(v.[Required],0)=0 or (v.[Required] = 1 and isnull(m.[Value],'') = isnull(v.[Match],'')))
            ) or
            k.[Required] = 0 and isnull(m.[Key],'') = isnull(k.[Match],'') or
            v.[Required] = 0 and isnull(m.[Value],'') = isnull(v.[Match],'')
        
        select [Id], [Key], [Value] from @tmptbl
        where row_id between @startRow and @endRow
    
        -- calculate the record count in all pages
        select @recordCount=COUNT(*) from @tmptbl
        -- calculate the page count
        set @pageCount = CEILING(@recordCount/CAST(@pageSize as float))
    end
RETURN 0

這里用了一個表變量，注意表變量是可被緩存的，臨時表沒有哦，用表變量不用with...as是因為后面在計算過濾后的總記錄數(shù)的時候，還需用一次過濾后的集合。這里我希望列Key和列Value都可以被過濾，于是用了兩個outer apply來將剛才那個函數(shù)的輸出表附加到每行上，在where比較的地方，先比較Required是1的必要條件，當(dāng)然如果針對某個column沒有rule的話，也就是required is null的情況，是需要排除的，最后再附加連個required=0的可選條件，這樣的話，一個select就可以把各種條件過濾出來了。不過，有個問題是，如果需要過濾的列比較多，那比較語句也要一條條加上去。

最后，來測試下：

我給表填充了這么些數(shù)據(jù)：

SET IDENTITY_INSERT [dbo].[Configuration] ON
INSERT [dbo].[Configuration] ([Id], [Key], [Value]) VALUES (1, N'test1', N'123')
INSERT [dbo].[Configuration] ([Id], [Key], [Value]) VALUES (2, N'test2', N'123')
INSERT [dbo].[Configuration] ([Id], [Key], [Value]) VALUES (3, N'test3', N'567')
INSERT [dbo].[Configuration] ([Id], [Key], [Value]) VALUES (4, N'test4', NULL)
INSERT [dbo].[Configuration] ([Id], [Key], [Value]) VALUES (5, N'test5', NULL)
INSERT [dbo].[Configuration] ([Id], [Key], [Value]) VALUES (6, N'test6', NULL)
INSERT [dbo].[Configuration] ([Id], [Key], [Value]) VALUES (7, N'test7', NULL)
INSERT [dbo].[Configuration] ([Id], [Key], [Value]) VALUES (8, N'test8', NULL)
INSERT [dbo].[Configuration] ([Id], [Key], [Value]) VALUES (9, N'test9', NULL)
INSERT [dbo].[Configuration] ([Id], [Key], [Value]) VALUES (10, N'test10', NULL)
INSERT [dbo].[Configuration] ([Id], [Key], [Value]) VALUES (11, N'test11', NULL)
SET IDENTITY_INSERT [dbo].[Configuration] OFF

測試腳本：

declare @pageIndex int; set @pageIndex=1;
declare @pageSize int;    set @pageSize=5;
declare @filter xml; 
set @filter='<filter><rule column="key" match="test3" required="1"/><rule column="value" match="123" required="0"/></filter>'
declare @pageCount int;
declare @recordCount int;

exec dbo.sp_r_fp_configuration @pageIndex,@pageSize,@filter,@pageCount=@pageCount OUTPUT, @recordCount=@recordCount OUTPUT
select @pageCount as [PAGECOUNT], @recordCount as [RECORDCOUNT]