SQL "How To's" Part 1
August 4, 2001
1) How to display Year as YYYY instead of YY
Enterprise Manager adopts the User's regional settings for the date format. By default, the regional setting for the short date format is m/d/yy. To display it in m/d/yyyy format, follow the following steps:
On the taskbar, click the Start button, point to Settings and then select Control Panel. In the Control Panel dialog box double-click Regional Settings. In the Regional Settings Properties dialog box, select the Date tab. Next, change the value for the Short Date Style from M/d/yy to M/d/yyyy.
2) How to Build a Comma Delimited String from Table values
Sometimes you might want to return your records in a single comma delimited string. For example, if you have records like :-
Instead of returning it as a recordset containing these 5 records, you might want to return them as 'Mango, Banana, Peach, Grapes, Strawberry'. Here's how you can accomplish this.
-- Create a temporary table & insert dummy records
Create Table #Fruits (Fruit Varchar(25)) Insert #Fruits (Fruit) values('Mango') Insert #Fruits (Fruit) values('Banana') Insert #Fruits (Fruit) values('Peach') Insert #Fruits (Fruit) values('Grapes') Insert #Fruits (Fruit) values('Strawberry')-- Build comma delimited string
Declare @Fruits Varchar(200) Set @Fruits = '' Update #Fruits Set @Fruits = @Fruits + Fruit + ',' Set @Fruits = Substring(@Fruits,1,len(@Fruits)-1) -- to remove extra comma at the end print @Fruits
3) How to write values to a Text file
To write a result of a SELECT query in a text file :-
master..xp_cmdshell 'osql -SMyServer -Umyuser -Pmypwd -Q"select * from products" -dNorthwind -w"1000" -oc:\MyText.txt'
To write a string (like comments, etc.) you can use this code :-
declare @cmd varchar(1000) select @cmd = 'echo These are the Products in the database>> "c:\MyText.txt"' exec master..xp_cmdshell @cmd
4) How to add a User Defined Error Message
Use Master Go EXEC sp_addmessage @msgnum = 50001, @severity = 16, @msgtext = N'Failed to insert Customer Transaction into %s table', @lang = 'us_english' Go
You can raise this message from your code like this :-
INSERT Customers (CustomerName) VALUES ('Rick Nelson') IF @@Error <> 0 RAISERROR (50001,16,1, 'Customers')
5) How to get the Rowcount as well as Error at the same time
Normally when we run a Query, we check if the query was executed successfully or not before commiting it.
DECLARE @CustomerId Int SET @CustomerId = 1 Begin Transaction Update Orders Set OrderDate = GetDate() Where CustomerId = @CustomerId IF @@Error <> 0 Begin Raiserror('Failed to update Orders',16,1) Rollback Transaction End Commit Transaction
But what if you also want to get the number of records which were effected by this query? If you do a @@Rowcount after your Error checking statement then you are going to get 0 as the value of @@Recordcount would have been reset. And if you place @@Recordcount before the error-checking statement then your @@Error would get reset. So what's the solution to get both of them at the same time ? Save both the values in a local variable and then check that local variable. Here's how it can be done.
DECLARE @Rcount Int DECLARE @ErrNum Int DECLARE @CustomerId Int SET @Rcount = 0 SET @ErrNum = 0 SET @CustomerId = 1 Begin Transaction Update Orders Set OrderDate = GetDate() Where CustomerId = @CustomerId SELECT @Rcount = @@RowCount, @ErrNum = @@Error -- check if there was an error in Updating the records IF @ErrNum <> 0 Begin Raiserror('Failed to update Orders',16,1) Rollback Transaction End -- check if some records were updated or not IF @Rcount = 0 Begin Raiserror('No records for CustomerId %d',16,1, @CustomerId) Rollback Transaction End Commit Transaction
Any comments or suggestions are welcome at firstname.lastname@example.org.