Question

Is possible to pass type as param in SQL function?

thank in advance.

Answer 1

the parameter type is defined within the function header, as a result it is always the same within the function. When you pass in a parameter that is a different types than the defined type parameter type, SQL Server does its best to that to the defined function parameter type.

I have a few functions that I want to work just like what you are after. The way I work around this issue is to define the function parameter as a varchar(x), and then issue any necessary CVONVERT() or formatting on the incoming parameter in the function call the parameter when you call it.

CREATE FUNCTION dbo.QuoteValue
(
     @InputStr      varchar(8000)  --value to format
)
RETURNS
varchar(8000)
AS
BEGIN
    RETURN COALESCE(''''+@InputStr+'''','null')
END
GO

DECLARE @DateValue  datetime
SET @DateValue=GETDATE()
PRINT '@DateValue='+dbo.QuoteValue(@DateValue)
PRINT '@DateValue='+dbo.QuoteValue(CONVERT(varchar,@DateValue,121))

Depending on what you are after, if you want to work with dates or numbers, make the function parameter varchar(x) and within the function use:

• ISDATE ( expression ) – ISDATE returns 1 if the input expression is a valid date; otherwise, it returns 0. The following table shows the return values for a selection of examples.
• ISNUMERIC (Transact-SQL) – ISNUMERIC returns 1 when the input expression evaluates to a valid integer, floating point number, money or decimal type; otherwise it returns 0. A return value of 1 indicates that expression can be converted to at least one of the numeric types.

here is an example of how to handle dates…

CREATE FUNCTION dbo.DateXYZ
(
     @InputStr      varchar(50)  --date value manipulate
)
RETURNS
datetime
AS
BEGIN
    DECLARE @DateValue  datetime

    IF ISDATE(@InputStr)=1
    BEGIN
        SET @DateValue=@InputStr
        --do some datetime manipulation here
    END  
    RETURN @DateValue --will return null if not given a valid date
END
GO

You could use it as follows:

DECLARE @X varchar(50)
DECLARE @Y varchar(50)
DECLARE @BadDate datetime
DECLARE @GoodDate datetime
SET @X='bad date!!'
SET @Y='1/1/2009'
SET @BadDate=dbo.DateXYZ(@X)
SET @GoodDate=dbo.DateXYZ(@Y)
SELECT @BadDate,@GoodDate

you could also pass in a parameter to signify what you are passing in:

CREATE FUNCTION dbo.AnyType
(
     @InputStr      varchar(8000)  --general purpose value
    ,@Type          char(1)         --"I"nt, "F"loat, "D"atetime, "S"tring, etc...
)
RETURNS
varchar(8000)
AS
BEGIN
    DECLARE @ReturnValue  varchar(8000)

    IF @Type='I' --int
    BEGIN
        DECLARE @IntValue int
        SET @IntValue=@InputStr
        --do some int manipulation here
        SET @ReturnValue=@IntValue
    END  
    ELSE IF @Type='F' --float
    BEGIN
        DECLARE @FloatValue float
        SET @FloatValue=@InputStr
        --do some float manipulation here
        SET @ReturnValue=@FloatValue
    END  
       ELSE IF @Type='D' --datetime
    BEGIN
        DECLARE @DatetimeValue  datetime
        SET @DatetimeValue=@InputStr
        --do some datetime manipulation here
        SET @ReturnValue=CONVERT(varchar(23),@DatetimeValue,121)
    END   
    --etc...
    --etc...

    RETURN @ReturnValue
END
GO

Functions can only return a single fixed type, make it varchar(x) and have the caller assign it to a variable of the the proper data type, or CAST it in a result set as necessary.