下面的 sql server 函数被转换为 mysql 但在 mysql 中，与 sql server 相比，子字符串以不同的方式工作，任何人都可以用相同的逻辑在 mysql 中执行它吗？
ALTER FUNCTION [dbo].[udf_Num_ToWords] (
@Number Numeric (38, 0) -- Input number with as many as 18 digits
) RETURNS VARCHAR(8000)
AS BEGIN
DECLARE @inputNumber VARCHAR(38)
DECLARE @NumbersTable TABLE (number CHAR(2), word VARCHAR(10))
DECLARE @outputString VARCHAR(8000)
DECLARE @length INT
DECLARE @counter INT
DECLARE @loops INT
DECLARE @position INT
DECLARE @chunk CHAR(3) -- for chunks of 3 numbers
DECLARE @tensones CHAR(2)
DECLARE @hundreds CHAR(1)
DECLARE @tens CHAR(1)
DECLARE @ones CHAR(1)
IF @Number = 0 Return 'Zero'
-- initialize the variables
SELECT @inputNumber = CONVERT(varchar(38), @Number)
, @outputString = ''
, @counter = 1
SELECT @length = LEN(@inputNumber)
, @position = LEN(@inputNumber) - 2
, @loops = LEN(@inputNumber)/3
-- make sure there is an extra loop added for the remaining numbers
IF LEN(@inputNumber) % 3 <> 0 SET @loops = @loops + 1
-- insert data for the numbers and words
INSERT INTO @NumbersTable SELECT '00', ''
UNION ALL SELECT '01', 'one' UNION ALL SELECT '02', 'two'
UNION ALL SELECT '03', 'three' UNION ALL SELECT '04', 'four'
UNION ALL SELECT '05', 'five' UNION ALL SELECT '06', 'six'
UNION ALL SELECT '07', 'seven' UNION ALL SELECT '08', 'eight'
UNION ALL SELECT '09', 'nine' UNION ALL SELECT '10', 'ten'
UNION ALL SELECT '11', 'eleven'UNION ALL SELECT '12', 'twelve'
UNION ALL SELECT '13', 'thirteen'UNION ALL SELECT '14', 'fourteen'
UNION ALL SELECT '15', 'fifteen' UNION ALL SELECT '16', 'sixteen'
UNION ALL SELECT '17', 'seventeen'UNION ALL SELECT '18', 'eighteen'
UNION ALL SELECT '19', 'nineteen'UNION ALL SELECT '20', 'twenty'
UNION ALL SELECT '30', 'thirty' UNION ALL SELECT '40', 'forty'
UNION ALL SELECT '50', 'fifty' UNION ALL SELECT '60', 'sixty'
UNION ALL SELECT '70', 'seventy' UNION ALL SELECT '80', 'eighty'
UNION ALL SELECT '90', 'ninety'
WHILE @counter <= @loops BEGIN
-- get chunks of 3 numbers at a time, padded with leading zeros
SET @chunk = RIGHT('000' + SUBSTRING(@inputNumber, @position, 3), 3)
IF @chunk <> '000' BEGIN
SELECT @tensones = SUBSTRING(@chunk, 2, 2)
, @hundreds = SUBSTRING(@chunk, 1, 1)
, @tens = SUBSTRING(@chunk, 2, 1)
, @ones = SUBSTRING(@chunk, 3, 1)
-- If twenty or less, use the word directly from @NumbersTable
IF CONVERT(INT, @tensones) <= 20 OR @Ones='0' BEGIN
SET @outputString = (SELECT word
FROM @NumbersTable
WHERE @tensones = number)
+ CASE @counter WHEN 1 THEN '' -- No name
WHEN 2 THEN ' thousand ' WHEN 3 THEN ' million '
WHEN 4 THEN ' billion ' WHEN 5 THEN ' trillion '
WHEN 6 THEN ' quadrillion ' WHEN 7 THEN ' quintillion '
WHEN 8 THEN ' sextillion ' WHEN 9 THEN ' septillion '
WHEN 10 THEN ' octillion ' WHEN 11 THEN ' nonillion '
WHEN 12 THEN ' decillion ' WHEN 13 THEN ' undecillion '
ELSE '' END
+ @outputString
END
ELSE BEGIN -- break down the ones and the tens separately
SET @outputString = ' '
+ (SELECT word
FROM @NumbersTable
WHERE @tens + '0' = number)
+ '-'
+ (SELECT word
FROM @NumbersTable
WHERE '0'+ @ones = number)
+ CASE @counter WHEN 1 THEN '' -- No name
WHEN 2 THEN ' thousand ' WHEN 3 THEN ' million '
WHEN 4 THEN ' billion ' WHEN 5 THEN ' trillion '
WHEN 6 THEN ' quadrillion ' WHEN 7 THEN ' quintillion '
WHEN 8 THEN ' sextillion ' WHEN 9 THEN ' septillion '
WHEN 10 THEN ' octillion ' WHEN 11 THEN ' nonillion '
WHEN 12 THEN ' decillion ' WHEN 13 THEN ' undecillion '
ELSE '' END
+ @outputString
END
-- now get the hundreds
IF @hundreds <> '0' BEGIN
SET @outputString = (SELECT word
FROM @NumbersTable
WHERE '0' + @hundreds = number)
+ ' hundred '
+ @outputString
END
END
SELECT @counter = @counter + 1
, @position = @position - 3
END
-- Remove any double spaces
SET @outputString = LTRIM(RTRIM(REPLACE(@outputString, ' ', ' ')))
SET @outputstring = UPPER(LEFT(@outputstring, 1)) +
SUBSTRING(@outputstring, 2, 8000)
RETURN @outputString -- return the result
END