A Cursor with the name already exists

 While executing cursor inside Stored procedure it is throwing error:

A cursor with the name 'cursorName' already exists

declare cursorName CURSOR FOR
        select ...;

    open cursorName;

        Body of cursor...
        close cursorName;
        deallocate cursorName;

This is because we are using global cursor that will be defined each time you are calling this procedure and give you the same error.

Define a local cursor. Just put the keyword LOCAL after CURSOR

This will look like

declare cursorName CURSOR LOCAL FOR
...
This will resolve the issue.

error while passing Datetime parameter in dynamic sql command

 I am using a dynamic query wherein I want to use the variable which holds the datetime, whenever I execute the query it says cannot convert datetime from string

Lets see using below example:

Declare @OrderDate Datetime
Declare @sql varchar(max)
set @OrderDate='2010-12-29'
set @sql='Select SalesAmount,taxamt,totalproductcost,orderdate from [dbo].[FactInternetSales]
where orderdate='''+@OrderDate+''''
exec (@sql)

Output:
Msg 241, Level 16, State 1, Line 8
Conversion failed when converting date and/or time from character string.

To resolve this we need to convert datetime variable. It looks like below.

Declare @OrderDate Datetime
Declare @sql varchar(max)
set @OrderDate='2010-12-29'
set @sql='Select SalesAmount,taxamt,totalproductcost,orderdate from [dbo].[FactInternetSales]
where orderdate='''+CONVERT(VARCHAR(10),@OrderDate, 101)+''''
exec (@sql)