在MySQL中將二進制字符串轉換爲bigint？

Question

我正在嘗試在MySQL中將字符串散列爲64位值（bigint）。我知道MD5（）函數，它返回一個128位散列作爲二進制字符串。我很樂意獲取這個結果的最低或最高64位。但是，我無法弄清楚如何從二進制字符串類型轉換爲任何類型的數字類型。任何指針？

Answer 1

使用CONV()函數MD5哈希轉換從基地16到基地10 CAST將其轉換爲一個數字：

select cast(conv(substring(md5(id), 1, 16), 16, 10) as unsigned integer) from SomeTable; 

Answer 2

CREATE FUNCTION dbo.HexStrToVarBinary(@hexstr varchar(8000)) 
RETURNS varbinary(8000) 
AS 
BEGIN 
    DECLARE @hex char(1), @i int, @place bigint, @a bigint 
    SET @i = LEN(@hexstr) 

    set @place = convert(bigint,1) 
    SET @a = convert(bigint, 0) 

    WHILE (@i > 0 AND (substring(@hexstr, @i, 1) like '[0-9A-Fa-f]')) 
    BEGIN 
     SET @hex = SUBSTRING(@hexstr, @i, 1) 
     SET @a = @a + 
    convert(bigint, CASE WHEN @hex LIKE '[0-9]' 
     THEN CAST(@hex as int) 
     ELSE CAST(ASCII(UPPER(@hex))-55 as int) end * @place) 
    set @place = @place * convert(bigint,16) 
     SET @i = @i - 1 

    END 

    RETURN convert(varbinary(8000),@a) 
END 
GO 

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