跨多个列搜索实现

Question

假设我有一张表:

Persons  
  FirstName varchar(50)  
  LastName varchar(50)
  EmailAddress varchar(200)  

现在,假设我有一个谷歌搜索框; 换句话说,只有一个文本框带有搜索按钮.

通常我们会这样做:

declare @searchTerm varchar(50)
set @searchTerm = 'tom'

select *
  from Persons
  where (FirstName = @searchTerm) 
     or (LastName = @searchTerm)
     or (EmailAddress = @searchTerm)

我想做的是能够将名字和姓氏(例如)传递给@searchTerm变量,但我的大脑只是不想构建那个查询.;)

例如:

declare @searchTerm varchar(50)
set @searchTerm = 'tom smith'

select *
  from Persons
  where ????

我们的想法是返回"tom"或"smith"出现在这些字段中的所有记录.

Answer 1

这是一个非常复杂的主题,具有许多微妙的性能影响.你真的需要阅读Erland Sommarskog撰写的这些优秀文章:

T-SQL中的动态搜索条件

动态SQL的诅咒与祝福

由于没有"一刀切"的查询方法,因此在执行此操作时会产生微妙的性能影响.如果你想超越只是让查询返回正确的答案,无论它有多慢,请看看这篇文章:Erland Sommarskog在T-SQL中的动态搜索条件.它涵盖了每种方法,并详细介绍了每种方法的PRO和Cons.

如果您可以确定搜索列的最小和最大可能范围,并且搜索列为NOT NULL,那么您可以做得比(@Search IS NULL或Col = @ Search)更好,请参阅上面链接的这个区域文章.但是你应该阅读整篇文章,有很多变化取决于你的情况,你真的需要学习多种方法以及何时使用它们.

如果要在单个字符串参数中搜索多个术语,则需要拆分该字符串.

您需要创建拆分功能.这是分割函数的使用方式:

SELECT
    *
    FROM YourTable                               y
    INNER JOIN dbo.yourSplitFunction(@Parameter) s ON y.ID=s.Value

我更喜欢使用数字表方法在TSQL中拆分字符串,但是有很多方法可以在SQL Server中拆分字符串,请参阅前面的链接,它解释了每个链接的PRO和CON.

要使Numbers Table方法起作用,您需要执行一次性表设置,这将创建一个Numbers包含1到10,000行的表:

SELECT TOP 10000 IDENTITY(int,1,1) AS Number
    INTO Numbers
    FROM sys.objects s1
    CROSS JOIN sys.objects s2
ALTER TABLE Numbers ADD CONSTRAINT PK_Numbers PRIMARY KEY CLUSTERED (Number)

设置Numbers表后,创建此拆分功能:

CREATE FUNCTION [dbo].[FN_ListToTable]
(
     @SplitOn  char(1)      --REQUIRED, the character to split the @List string on
    ,@List     varchar(8000)--REQUIRED, the list to split apart
)
RETURNS TABLE
AS
RETURN 
(

    ----------------
    --SINGLE QUERY-- --this will not return empty rows
    ----------------
    SELECT
        ListValue
        FROM (SELECT
                  LTRIM(RTRIM(SUBSTRING(List2, number+1, CHARINDEX(@SplitOn, List2, number+1)-number - 1))) AS ListValue
                  FROM (
                           SELECT @SplitOn + @List + @SplitOn AS List2
                       ) AS dt
                      INNER JOIN Numbers n ON n.Number < LEN(dt.List2)
                  WHERE SUBSTRING(List2, number, 1) = @SplitOn
             ) dt2
        WHERE ListValue IS NOT NULL AND ListValue!=''

);
GO 

您现在可以轻松地将CSV字符串拆分为表格并加入其中:

select * from dbo.FN_ListToTable(',','1,2,3,,,4,5,6777,,,')

OUTPUT:

ListValue
-----------------------
1
2
3
4
5
6777

(6 row(s) affected)

您可以使用多个搜索条件字符串,如下所示:

DECLARE @Persons table (FirstName varchar(50)  ,  LastName varchar(50),  EmailAddress varchar(200) )
INSERT INTO @Persons VALUES ('aaa','bbb','ccc@ddd.eee')
INSERT INTO @Persons VALUES ('xxx','yyy','zzz@abbba.zzz')
INSERT INTO @Persons VALUES ('aaa','yyy','zzz@zzz.zzz')
INSERT INTO @Persons VALUES ('111','222','333@444.555')

declare @searchTerm varchar(50)
set @searchTerm = 'aaa bbb'

--this should use an index on FirstName and LastName if they exist, no index usage on EmailAddress
select
    p.*  --<<"*" isn't good, only list the columns you need
    FROM @Persons                                      p
        INNER JOIN dbo.FN_ListToTable(' ',@searchTerm) b on p.FirstName=b.Listvalue
UNION
select
    p.*  --<<"*" isn't good, only list the columns you need
    FROM @Persons                                      p
        INNER JOIN dbo.FN_ListToTable(' ',@searchTerm) b on p.LastName=b.Listvalue
UNION
select
    p.*  --<<"*" isn't good, only list the columns you need
    FROM @Persons                                      p
        INNER JOIN dbo.FN_ListToTable(' ',@searchTerm) b on p.EmailAddress like '%'+b.Listvalue+'%'

OUTPUT:

FirstName  LastName   EmailAddress
---------- ---------- -------------------------
aaa        bbb        ccc@ddd.eee
aaa        yyy        zzz@zzz.zzz
xxx        yyy        zzz@abbba.zzz

(3 row(s) affected)

此方法适用于任意数量的参数:

aaa
 aaa
aaa bbb
aaa  bbb
aaa bbb eee
aaa bbb eee ddd
aaa   bbb   eee