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.

Answer 2

In this part of your SP:

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

you are trying to concatenate strings and datetimes.

As the datetime type has higher priority than varchar/nvarchar, the + operator, when it happens between a string and a datetime, is interpreted as addition, not as concatenation, and the engine then tries to convert your string parts (' or convert (Date,DateLog) >= ''' and others) to datetime or numeric values. And fails.

That doesn't happen if you omit the last two parameters when invoking the procedure, because the condition evaluates to false and the offending statement isn't executed.

To amend the situation, you need to add explicit casting of your datetime variables to strings:

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

You'll also need to add closing single quotes:

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