¡Hola, chicos!
El 07/04 vi una pregunta en un grupo de Whatsapp sobre la posibilidad de que SQL Server tenga una función nativa para escribir números en palabras, la cual no existe.

Empecé a buscar algunas funciones T-SQL en Internet que hicieran esto y solo pude encontrar una función que puede cumplir con este objetivo y me gustaría compartir con ustedes una versión modificada de esta función (enlace de función original) que mejoré el código e hice algunas correcciones, además de crear una versión en inglés de esta función también.

Versión portuguesa:

Con esta función, será fácil devolver números en forma extendida, con o sin moneda. Consulte el código a continuación y algunos ejemplos para comprender cómo utilizar esta función en su vida diaria:

CREATE OR ALTER FUNCTION dbo.fncNumeroPorExtenso (
    @valor DECIMAL(20, 2),
    @incluirMoeda BIT
)
RETURNS VARCHAR(8000)
AS
BEGIN

    ---------------------------------------
    -- Define as variáveis
    ---------------------------------------

    DECLARE 
        @valorCentavos TINYINT = CONVERT(INT, (ABS(@valor) - CONVERT(BIGINT, ABS(@valor))) * 100),
        @valorStr VARCHAR(20) = CONVERT(VARCHAR(20), CONVERT(BIGINT, ABS(@valor))),
        @pedacoStr1 VARCHAR(20),
        @pedacoStr2 VARCHAR(20),
        @pedacoStr3 VARCHAR(20),
        @valorInt BIGINT = CONVERT(BIGINT, ABS(@valor)),
        @pedacoInt1 INT,
        @pedacoInt2 INT,
        @pedacoInt3 INT,
        @menorNumero INT,
        @retorno VARCHAR(8000) = '';


    IF (@valor = 0)
    BEGIN
        SET @retorno = 'Zero' + (CASE WHEN @incluirMoeda = 1 THEN ' Reais' ELSE '' END);
        RETURN @retorno;
    END;


    ---------------------------------------
    -- Cria as tabelas com os intervalos
    ---------------------------------------

    DECLARE @tabelaNumeros TABLE
    (
        descricao VARCHAR(50) NOT NULL,
        menor INT NOT NULL,
        maior INT NOT NULL
    );

    DECLARE @tabelaMilhares TABLE
    (
        descricaoUm VARCHAR(50) NOT NULL,
        descricaoPl VARCHAR(50) NOT NULL,
        menor INT NOT NULL,
        maior INT NOT NULL
    );


    INSERT INTO @tabelaNumeros
    VALUES
        ( 'Um', 1, 1 ), 
        ( 'Dois', 2, 2 ), 
        ( 'Três', 3, 3 ), 
        ( 'Quatro', 4, 4 ), 
        ( 'Cinco', 5, 5 ), 
        ( 'Seis', 6, 6 ), 
        ( 'Sete', 7, 7 ), 
        ( 'Oito', 8, 8 ), 
        ( 'Nove', 9, 9 ), 
        ( 'Dez', 10, 10 ), 
        ( 'Onze', 11, 11 ), 
        ( 'Doze', 12, 12 ), 
        ( 'Treze', 13, 13 ), 
        ( 'Catorze', 14, 14 ), 
        ( 'Quinze', 15, 15 ), 
        ( 'Dezesseis', 16, 16 ), 
        ( 'Dezessete', 17, 17 ), 
        ( 'Dezoito', 18, 18 ), 
        ( 'Dezenove', 19, 19 ), 
        ( 'Vinte', 20, 20 ), 
        ( 'Vinte e', 21, 29 ), 
        ( 'Trinta', 30, 30 ), 
        ( 'Trinta e', 31, 39 ), 
        ( 'Quarenta', 40, 40 ), 
        ( 'Quarenta e', 41, 49 ), 
        ( 'Cinquenta', 50, 50 ), 
        ( 'Cinquenta e', 51, 59 ), 
        ( 'Sessenta', 60, 60 ), 
        ( 'Sessenta e', 61, 69 ), 
        ( 'Setenta', 70, 70 ), 
        ( 'Setenta e', 71, 79 ), 
        ( 'Oitenta', 80, 80 ), 
        ( 'Oitenta e', 81, 89 ), 
        ( 'Noventa', 90, 90 ), 
        ( 'Noventa e', 91, 99 ), 
        ( 'Cem', 100, 100 ), 
        ( 'Cento e', 101, 199 ), 
        ( 'Duzentos', 200, 200 ), 
        ( 'Duzentos e', 201, 299 ), 
        ( 'Trezentos', 300, 300 ), 
        ( 'Trezentos e', 301, 399 ), 
        ( 'Quatrocentos', 400, 400 ), 
        ( 'Quatrocentos e', 401, 499 ), 
        ( 'Quinhentos', 500, 500 ), 
        ( 'Quinhentos e', 501, 599 ), 
        ( 'Seiscentos', 600, 600 ), 
        ( 'Seiscentos e', 601, 699 ), 
        ( 'Setecentos', 700, 700 ), 
        ( 'Setecentos e', 701, 799 ), 
        ( 'Oitocentos', 800, 800 ), 
        ( 'Oitocentos e', 801, 899 ), 
        ( 'Novecentos', 900, 900 ), 
        ( 'Novecentos e', 901, 999 );


    INSERT INTO @tabelaMilhares
    VALUES
        ('Mil', 'Mil', 4, 6),
        ('Milhão', 'Milhões', 7, 9),
        ('Bilhão', 'Bilhões', 10, 12),
        ('Trilhão', 'Trilhões', 13, 15),
        ('Quatrilhão', 'Quatrilhões', 16, 18);


    ---------------------------------------
    -- Gera os valores por extenso dos reais
    ---------------------------------------

    -- Busca o número de casas
    SELECT TOP(1)
        @menorNumero = menor - 1
    FROM 
        @tabelaMilhares
    WHERE
        menor > LEN(@valorStr);


    -- Adiciona casas a esquerda (tratando sempre de 3 em 3 casas)
    SET @valorStr = REPLICATE('0', @menorNumero - LEN(@valorStr)) + @valorStr;


    -- Loop para converter por extenso por cada bloco de 3 casas
    WHILE (LEN(@valorStr) > 0)
    BEGIN

        -- Atribui em variáveis os caracteres do bloco de 3 em 3
        SET @pedacoStr1 = LEFT(@valorStr, 3)
        SET @pedacoStr2 = RIGHT(@pedacoStr1, 2)
        SET @pedacoStr3 = RIGHT(@pedacoStr2, 1)

        SELECT 
            @pedacoInt1 = CONVERT(INT, @pedacoStr1),
            @pedacoInt2 = CONVERT(INT, @pedacoStr2),
            @pedacoInt3 = CONVERT(INT, @pedacoStr3)


        -- Busca a centena
        SELECT 
            @retorno += descricao + ' '
        FROM 
            @tabelaNumeros
        WHERE 
            (
                LEN(@pedacoInt1) = 3
                AND @pedacoStr1 BETWEEN menor AND maior
            )
            OR (
                @pedacoInt2 <> 0
                AND LEN(@pedacoInt2) = 2
                AND @pedacoInt2 BETWEEN menor AND maior
            )
            OR (
                @pedacoInt3 <> 0
                AND ( @pedacoInt2 < 10 OR @pedacoInt2 > 20 )
                AND @pedacoInt3 BETWEEN menor AND maior
            )
        ORDER BY 
            maior DESC;


        -- Define o milhar (se foi escrito algum valor para ele)
        IF (@pedacoInt1 > 0)
        BEGIN

            SELECT 
                @retorno += (CASE WHEN @pedacoInt1 > 1 THEN descricaoPl ELSE descricaoUm END)
            FROM
                @tabelaMilhares
            WHERE 
                LEN(@valorStr) BETWEEN menor AND maior

        END


        -- Remove os pedaços efetuados
        SET @valorStr = RIGHT(@valorStr, LEN(@valorStr) - 3);


        IF (CONVERT(INT, LEFT(@valorStr, 3)) > 0)
            SET @retorno += ', ';
        ELSE IF (CONVERT(INT, @valorStr) = 0 AND LEN(@valorStr) = 6)
            SET @retorno += ' de ';


    END;


    -- Somente coloca se tiver algum valor.
    IF (LEN(@retorno) > 0 AND @incluirMoeda = 1)
        SET @retorno += (CASE WHEN RIGHT(@retorno, 1) <> ' ' THEN ' ' ELSE '' END) + (CASE WHEN @valorInt > 1 THEN 'Reais ' ELSE 'Real ' END);



    ---------------------------------------
    -- Gera os centavos
    ---------------------------------------

    SET @valorStr = CONVERT(VARCHAR(2), @valorCentavos);


    -- Adiciona casas a esquerda
    SET @valorStr = REPLICATE('0', 2 - LEN(@valorStr)) + @valorStr;
    SET @pedacoStr1 = @valorStr;
    SET @pedacoStr2 = RIGHT(@valorStr, 1);

    SELECT 
        @pedacoInt1 = CONVERT(INT, @pedacoStr1),
        @pedacoInt2 = CONVERT(INT, @pedacoStr2);


    -- Adiciona o separador de centavos (se houver)
    IF (@pedacoInt1 > 0 AND (LEN(@retorno) > 0))
        SET @retorno += 'e ';


    -- Gera o extenso dos centavos
    SELECT 
        @retorno += descricao + ' '
    FROM
        @tabelaNumeros
    WHERE 
        (
            @pedacoInt1 <> 0
            AND LEN(@pedacoInt1) = 2
            AND @pedacoInt1 BETWEEN menor AND maior
        )
        OR (  
            @pedacoInt2 <> 0
            AND (
                @pedacoInt1 < 10
                OR @pedacoInt1 > 20
            )
            AND @pedacoInt2 BETWEEN menor AND maior
        )
    ORDER BY 
        maior DESC;


    -- Coloca os centavos no plural ou não
    IF (@pedacoInt1 > 0 AND @incluirMoeda = 1)
        SELECT @retorno += 'Centavo' + (CASE WHEN @pedacoInt1 > 1 THEN 's' ELSE '' END)


    RETURN @retorno;


END;
GO

Ejemplos de uso – Con moneda:

SELECT
    dbo.fncNumeroPorExtenso(0, 1),
    dbo.fncNumeroPorExtenso(10, 1),
    dbo.fncNumeroPorExtenso(100, 1),
    dbo.fncNumeroPorExtenso(1000, 1),
    dbo.fncNumeroPorExtenso(100000, 1),
    dbo.fncNumeroPorExtenso(100000000, 1),
    dbo.fncNumeroPorExtenso(1234, 1),
    dbo.fncNumeroPorExtenso(123456, 1),
    dbo.fncNumeroPorExtenso(1234567890, 1)

SELECT
    dbo.fncNumeroPorExtenso(1234.99, 1),
    dbo.fncNumeroPorExtenso(4321.991234, 1),
    dbo.fncNumeroPorExtenso(12345678901.991234, 1)

SELECT
    dbo.fncNumeroPorExtenso(123456789.991234, 1),
    dbo.fncNumeroPorExtenso(12345678901.991234, 1)

Resultado:

Ejemplos de uso – SIN moneda:

SELECT
    dbo.fncNumeroPorExtenso(0, 0),
    dbo.fncNumeroPorExtenso(10, 0),
    dbo.fncNumeroPorExtenso(100, 0),
    dbo.fncNumeroPorExtenso(1000, 0),
    dbo.fncNumeroPorExtenso(100000, 0),
    dbo.fncNumeroPorExtenso(100000000, 0),
    dbo.fncNumeroPorExtenso(1234, 0),
    dbo.fncNumeroPorExtenso(123456, 0),
    dbo.fncNumeroPorExtenso(1234567890, 0)

SELECT
    dbo.fncNumeroPorExtenso(1234.99, 0),
    dbo.fncNumeroPorExtenso(4321.991234, 0),
    dbo.fncNumeroPorExtenso(12345678901.991234, 0)

SELECT
    dbo.fncNumeroPorExtenso(123456789.991234, 0),
    dbo.fncNumeroPorExtenso(12345678901.991234, 0)

Resultado:

versión en inglés

Si necesita devolver el número completo en inglés, también puede utilizar esta versión adaptada del script anterior.

CREATE FUNCTION dbo.fncFullNumber (
    @value DECIMAL(20, 2),
    @includeCurrency BIT = 1
)
RETURNS VARCHAR(8000)
AS
BEGIN

    ---------------------------------------
    -- Define variables
    ---------------------------------------

    DECLARE 
        @valueCents TINYINT = CONVERT(INT, (ABS(@value) - CONVERT(BIGINT, ABS(@value))) * 100),
        @valueStr VARCHAR(20) = CONVERT(VARCHAR(20), CONVERT(BIGINT, ABS(@value))),
        @chunkStr1 VARCHAR(20),
        @chunkStr2 VARCHAR(20),
        @chunkStr3 VARCHAR(20),
        @valueInt BIGINT = CONVERT(BIGINT, ABS(@value)),
        @chunkInt1 INT,
        @chunkInt2 INT,
        @chunkInt3 INT,
        @lowestNumber INT,
        @counter INT = 1,
        @numberOfChunks INT,
        @return VARCHAR(8000) = '';

    SET @numberOfChunks = LEN(@valueInt) / 3


    IF (@value = 0)
    BEGIN
        SET @return = 'Zero' + (CASE WHEN @includeCurrency = 1 THEN ' Dollars' ELSE '' END);
        RETURN @return;
    END;


    ---------------------------------------
    -- Creates tables with ranges
    ---------------------------------------

    DECLARE @tableNumbers TABLE
    (
        [description] VARCHAR(50) NOT NULL,
        [lower] INT NOT NULL,
        [higher] INT NOT NULL
    );

    DECLARE @tableThousands TABLE
    (
        descriptionSingular VARCHAR(50) NOT NULL,
        descriptionPlural VARCHAR(50) NOT NULL,
        [lower] INT NOT NULL,
        [higher] INT NOT NULL
    );


    INSERT INTO @tableNumbers
    VALUES
        ('One', 1, 1),
        ('Two', 2, 2),
        ('Three', 3, 3),
        ('Four', 4, 4),
        ('Five', 5, 5),
        ('Six', 6, 6),
        ('Seven', 7, 7),
        ('Eight', 8, 8),
        ('Nine', 9, 9),
        ('Ten', 10, 10),
        ('Eleven', 11, 11),
        ('Twelve', 12, 12),
        ('Thirteen', 13, 13),
        ('Fourteen', 14, 14),
        ('Fifteen', 15, 15),
        ('Sixteen', 16, 16),
        ('Seventeen', 17, 17),
        ('Eighteen', 18, 18),
        ('Nineteen', 19, 19),
        ('Twenty', 20, 20),
        ('Twenty-', 21, 29),
        ('Thirty', 30, 30),
        ('Thirty-', 31, 39),
        ('Forty', 40, 40),
        ('Forty-', 41, 49),
        ('Fifty', 50, 50),
        ('Fifty-', 51, 59),
        ('Sixty', 60, 60),
        ('Sixty-', 61, 69),
        ('Seventy', 70, 70),
        ('Seventy-', 71, 79),
        ('Eighty', 80, 80),
        ('Eighty-', 81, 89),
        ('Ninety', 90, 90),
        ('Ninety-', 91, 99),
        ('A Hundred', 100, 100),
        ('One hundred ', 101, 199),
        ('Two hundred', 200, 200),
        ('Two hundred and ', 201, 299),
        ('Three hundred', 300, 300),
        ('Three hundred and ', 301, 399),
        ('Four hundred', 400, 400),
        ('Four hundred and ', 401, 499),
        ('Five hundred', 500, 500),
        ('Five hundred and ', 501, 599),
        ('Six hundred', 600, 600),
        ('Six hundred and ', 601, 699),
        ('Seven hundred', 700, 700),
        ('Seven hundred and ', 701, 799),
        ('Eight hundred', 800, 800),
        ('Eight hundred and ', 801, 899),
        ('Nine hundred', 900, 900),
        ('Nine hundred and ', 901, 999);


    INSERT INTO @tableThousands
    VALUES
        ('Thousand', 'Thousand', 4, 6),
        ('Million', 'Millions', 7, 9),
        ('Billion', 'Billion', 10, 12),
        ('Trillion', 'Trillions', 13, 15),
        ('Quadrillion', 'Quadrillions', 16, 18);

    
    ---------------------------------------
    -- Generates the full values
    ---------------------------------------

    SELECT TOP(1)
        @lowestNumber = [lower] - 1
    FROM 
        @tableThousands
    WHERE
        [lower] > LEN(@valueStr);


    SET @valueStr = REPLICATE('0', @lowestNumber - LEN(@valueStr)) + @valueStr;


    WHILE (LEN(@valueStr) > 0)
    BEGIN

        SET @chunkStr1 = LEFT(@valueStr, 3)
        SET @chunkStr2 = RIGHT(@chunkStr1, 2)
        SET @chunkStr3 = RIGHT(@chunkStr2, 1)

        SELECT 
            @chunkInt1 = CONVERT(INT, @chunkStr1),
            @chunkInt2 = CONVERT(INT, @chunkStr2),
            @chunkInt3 = CONVERT(INT, @chunkStr3)


        SELECT 
            @return += [description] + ''
        FROM 
            @tableNumbers
        WHERE 
            (
                LEN(@chunkInt1) = 3
                AND @chunkStr1 BETWEEN [lower] AND [higher]
            )
            OR (
                @chunkInt2 <> 0
                AND LEN(@chunkInt2) = 2
                AND @chunkInt2 BETWEEN [lower] AND [higher]
            )
            OR (
                @chunkInt3 <> 0
                AND ( @chunkInt2 < 10 OR @chunkInt2 > 20 )
                AND @chunkInt3 BETWEEN [lower] AND [higher]
            )
        ORDER BY 
            [higher] DESC;


        IF (@chunkInt1 > 0)
        BEGIN
            
            SELECT 
                @return += ' ' + (CASE WHEN @chunkInt1 > 1 THEN descriptionPlural ELSE descriptionSingular END)
            FROM
                @tableThousands
            WHERE 
                LEN(@valueStr) BETWEEN [lower] AND [higher]

        END

        
        SET @valueStr = RIGHT(@valueStr, LEN(@valueStr) - 3);


        IF (CONVERT(INT, LEFT(@valueStr, 3)) > 0)
            SET @return += ', ';
        ELSE IF (CONVERT(INT, @valueStr) = 0 AND LEN(@valueStr) = 6)
            SET @return += ' of ';


        ---- Add an "and" expression on the last chunk
        --IF (@counter = @numberOfChunks AND CONVERT(INT, LEFT(@valueStr, 3)) > 0)
        --	SET @return += 'and '

        
        SET @counter += 1


    END;


    IF (LEN(@return) > 0)
    BEGIN
    
        IF (@includeCurrency = 1)
            SET @return += (CASE WHEN RIGHT(@return, 1) <> ' ' THEN ' ' ELSE '' END) + (CASE WHEN @valueInt > 1 THEN 'Dollars ' ELSE 'Dollar ' END);
        ELSE
            SET @return += ' '

    END



    ---------------------------------------
    -- Generate the decimal part
    ---------------------------------------

    SET @valueStr = CONVERT(VARCHAR(2), @valueCents);


    SET @valueStr = REPLICATE('0', 2 - LEN(@valueStr)) + @valueStr;
    SET @chunkStr1 = @valueStr;
    SET @chunkStr2 = RIGHT(@valueStr, 1);

    SELECT 
        @chunkInt1 = CONVERT(INT, @chunkStr1),
        @chunkInt2 = CONVERT(INT, @chunkStr2);


    IF (@chunkInt1 > 0 AND (LEN(@return) > 0))
        SET @return += 'and ';


    SELECT 
        @return += [description] + ''
    FROM
        @tableNumbers
    WHERE 
        (
            @chunkInt1 <> 0
            AND LEN(@chunkInt1) = 2
            AND @chunkInt1 BETWEEN [lower] AND [higher]
        )
        OR (
            @chunkInt2 <> 0
            AND (
                @chunkInt1 < 10
                OR @chunkInt1 > 20
            )
            AND @chunkInt2 BETWEEN [lower] AND [higher]
        )
    ORDER BY 
        [higher] DESC;


    IF (@chunkInt1 > 0 AND @includeCurrency = 1)
        SELECT @return += ' Cent' + (CASE WHEN @chunkInt1 > 1 THEN 's' ELSE '' END)


    RETURN @return;


END;

Ejemplos de uso – Con moneda:

SELECT
    dbo.fncFullNumber(0, 1),
    dbo.fncFullNumber(10, 1),
    dbo.fncFullNumber(100, 1),
    dbo.fncFullNumber(1000, 1),
    dbo.fncFullNumber(100000, 1),
    dbo.fncFullNumber(100000000, 1),
    dbo.fncFullNumber(1234, 1),
    dbo.fncFullNumber(123456, 1),
    dbo.fncFullNumber(1234567890, 1)

SELECT
    dbo.fncFullNumber(1234.99, 1),
    dbo.fncFullNumber(4321.991234, 1),
    dbo.fncFullNumber(12345678901.991234, 1)

SELECT
    dbo.fncFullNumber(123456789.991234, 1),
    dbo.fncFullNumber(12345678901.991234, 1)

Resultado:

Ejemplos de uso – SIN moneda:

SELECT
    dbo.fncFullNumber(0, 0),
    dbo.fncFullNumber(10, 0),
    dbo.fncFullNumber(100, 0),
    dbo.fncFullNumber(1000, 0),
    dbo.fncFullNumber(100000, 0),
    dbo.fncFullNumber(100000000, 0),
    dbo.fncFullNumber(1234, 0),
    dbo.fncFullNumber(123456, 0),
    dbo.fncFullNumber(1234567890, 0)

SELECT
    dbo.fncFullNumber(1234.99, 0),
    dbo.fncFullNumber(4321.991234, 0),
    dbo.fncFullNumber(12345678901.991234, 0)

SELECT
    dbo.fncFullNumber(123456789.991234, 0),
    dbo.fncFullNumber(12345678901.991234, 0)

Resultado:

¡Y eso es todo, amigos!
Espero que te haya gustado este tip y que te sea útil en tus proyectos.

¡Un abrazo grande y hasta la próxima!