Type datetime for input parameter in procedure

Question

I have created a procedure with this structure but it doesn't work for datetime input parameter

I executed this query but

declare @a datetime
declare @b datetime 

set @a='2012/04/06 12:23:45'
set @b='2012/08/06 21:10:12'

exec LogProcedure 'AccountLog', N'test', @a, @b

but SQL Server got me this error

Conversion failed when converting date and/or time from character string.

but when I test with this query it works

  exec LogProcedure 'AccountLog',N'test'

Stored procedure code:

alter PROCEDURE LogProcedure
    @TableName VARCHAR(60),
    @SearchString NVARCHAR(50),
    @DateFirst DateTime = '',
    @DateLast DateTime = ''
AS
BEGIN
    SET NOCOUNT ON

    DECLARE @FinalSQL      NVARCHAR(MAX)

    SET @FINALSQL = 'SELECT * FROM [' + @TableName + '] where 1=2  '

    IF @DateFirst <> '' and @DateLast <> ''
       set @FinalSQL  = @FinalSQL + '  or convert (Date,DateLog) >=     '''+@DateFirst + ' and convert (Date,DateLog) <='''+@DateLast  

    SELECT 
       @FinalSQL  = @FinalSQL + ' or  [' + SYSCOLUMNS.NAME + '] LIKE N''%' + @SearchString + '%'' ' 
    FROM SYSCOLUMNS 
    WHERE OBJECT_NAME(id) = @TableName
    AND TYPE_NAME(SYSCOLUMNS.XTYPE) IN ('VARCHAR','NVARCHAR','CHAR','NCHAR','INT','DECIMAL')
    ORDER BY COLID

    EXEC(@FinalSQL)
END 

This query is true too

SELECT * 
FROM AccountLog 
where 1=2  or convert (Date, DateLog) >= '2012/04/06' 
and convert (Date, DateLog) <='2012/08/06'

Answer 1

You should use the ISO-8601 format for string representations of dates - anything else is dependent on the SQL Server language and dateformat settings.

The ISO-8601 format for a DATETIME when using only the date is: YYYYMMDD (no dashes or antyhing!)

For a DATETIME with the time portion, it's YYYY-MM-DDTHH:MM:SS (with dashes, and a T in the middle to separate date and time portions).

If you want to convert a string to a DATE for SQL Server 2008 or newer, you can use YYYY-MM-DD (with the dashes) to achieve the same result. And don't ask me why this is so inconsistent and confusing - it just is, and you'll have to work with that for now.

So in your case, you should try:

declare @a datetime
declare @b datetime 

set @a = '2012-04-06T12:23:45'   -- 6th of April, 2012
set @b = '2012-08-06T21:10:12'   -- 6th of August, 2012

exec LogProcedure 'AccountLog', N'test', @a, @b

Furthermore - your stored proc has problem, since you're concatenating together datetime and string into a string, but you're not converting the datetime to string first, and also, you're forgetting the close quotes in your statement after both dates.

So change this line here to this:

IF @DateFirst <> '' and @DateLast <> ''
   SET @FinalSQL  = @FinalSQL + '  OR CONVERT(Date, DateLog) >= ''' + 
                    CONVERT(VARCHAR(50), @DateFirst, 126) +   -- convert @DateFirst to string for concatenation!
                    ''' AND CONVERT(Date, DateLog) <=''' +  -- you need closing quotes after @DateFirst!
                    CONVERT(VARCHAR(50), @DateLast, 126) + ''''      -- convert @DateLast to string and also: closing tags after that missing!

With these settings, and once you've fixed your stored procedure which contains problems right now, it will work.