从 T-SQL 中的字符串中提取最大数

Question

我正在导入从 excel 文件导入的数据。有一列的字符串可以包含多个数字。我正在尝试提取字符串中的最大数字，如果没有字符串则为 0。字符串的格式类似于： “100% post-消费者回收纸，50%post-消费者回收封面，90%post-消费者回收线。” "Paper contains 30% post-consumer content." 或者有时是一个空字符串或 null。

鉴于字符串格式不规则，我遇到了问题，如有任何帮助，我们将不胜感激。

Answer 1

按原样将数据拉入 SQL
编写查询以获取该列中不同的选项列表
添加一个新列来存储所需的值
编写更新语句来填充新列

至于确定最大尺寸，我认为您需要先查看您的数据集，但更新可以像这样简单：

DECLARE @COUNTER INT=1000
While EXISTS (SELECT * FROM <Table> WHERE NewColumn is NULL) AND @COUNTER>=0
BEGIN
   UPDATE <Table> SET NewColumn=@COUNTER WHERE <SearchColumn> LIKE '%' + CONVERT(VARCHAR,@COUNTER) + '%' AND NewColumn is NULL

   SET @COUNTER=@COUNTER-1
END

Answer 2

这是一个标量函数，它将一个字符串作为输入，return 它找到的最大整数（最多 3 位数字，但根据你的问题我假设你正在处理百分比。如果您需要更多数字，请无限重复 IF 语句。

将其粘贴到 SSMS 中并运行以创建函数。要调用它，请执行以下操作：

SELECT dbo.GetLargestNumberFromString(MyStringField) as [Largest Number in String]
FROM MyMessedUpData

函数：

CREATE FUNCTION GetLargestNumberFromString
(
@s varchar(max)
) 
RETURNS int
AS
BEGIN

    DECLARE @LargestNumber int, @i int
    SET @i = 1
    SET @LargestNumber = 0

    WHILE @i <= LEN(@s)
    BEGIN

    IF SUBSTRING(@s, @i, 3) like '[0-9][0-9][0-9]'
        BEGIN
            IF  CAST(SUBSTRING(@s, @i,3) as int) > @LargestNumber OR @LargestNumber IS NULL
            SET @LargestNumber = CAST(SUBSTRING(@s, @i,3) as int);
        END

    IF SUBSTRING(@s, @i, 2) like '[0-9][0-9]'
        BEGIN
            IF  CAST(SUBSTRING(@s, @i,2) as int) > @LargestNumber OR @LargestNumber IS NULL
            SET @LargestNumber = CAST(SUBSTRING(@s, @i,2) as int);
        END

    IF SUBSTRING(@s, @i, 1) like '[0-9]' OR @LargestNumber IS NULL
        BEGIN
            IF  CAST(SUBSTRING(@s, @i,1) as int) > @LargestNumber
            SET @LargestNumber = CAST(SUBSTRING(@s, @i,1) as int);
        END

    SET @i = @i + 1


    CONTINUE
    END
    RETURN @LargestNumber
END

Answer 3

SQL Fiddle Demo

生成 txt 的 LEN(txt) 个可能的 RIGHT() 片段。 Trim 每个片段的第一个非数字字符。测试余数是否为 int。 Return MAX().

SELECT
  txt
 ,MAX(TRY_CONVERT(int,LEFT(RIGHT(txt,i),PATINDEX('%[^0-9]%',RIGHT(txt,i)+' ')-1)))
FROM MyTable
CROSS APPLY (
  SELECT TOP(LEN(txt)) ROW_NUMBER() OVER(ORDER BY (SELECT NULL)) i FROM master.dbo.spt_values a, master.dbo.spt_values b
) x
GROUP BY txt

Answer 4

我最终创建了一个处理它的函数。这是代码：

CREATE FUNCTION [dbo].[cal_GetMaxPercentFromString] 

RETURNS float
AS
BEGIN
    declare @Numbers Table(number float)
    insert into @Numbers
    Select 0

    declare @temp as varchar(2000) = @string
    declare @position int, @length int, @offset int

    WHILE CHARINDEX('%', @temp) > 0
    BEGIN
        set @position = CHARINDEX('%', @temp)
        set @offset = 1
        set @length = -1
        WHILE @position - @offset > 0 and @length < 0
        BEGIN
            if SUBSTRING(@temp, @position - @offset, 1) not LIKE '[0-9]'
                set @length = @offset - 1    
            set @offset = @offset + 1
        END

        if @length > 0
        BEGIN
            insert into @Numbers
            select CAST(SUBSTRING(@temp, @position - @length, @length) as float)            
        END
        set @temp = SUBSTRING(@temp, 1, @position - 1) + SUBSTRING(@temp, @position + 1, LEN(@temp) - @position)
    END

    declare @return as float
    select @return = MAX(number) from @Numbers
    return @return
END

从 T-SQL 中的字符串中提取最大数

Extract largest number from a string in T-SQL

sql

tsql

sql-server

extraction

string-matching