How to Fix SQL Server Trigger Not Updating Issue

sql serversql-server-2000t-sqltrigger

Do I have an issue with my syntax? I created this trigger as sometimes the sales personnel forget to input the sale date (I Know it should be automatically captured which is an update in progress) but we are still seeing a few rows in the table with a null value for saledate Is this accurate syntax to update the field saledate with GetDate() when saledate is null? And I want to run this on Insert Or Update

create trigger updatefield
on salerecords
for insert, update
as
begin
  update salerecords
  set saledate = getdate()
  where saledate Is null
end

Best Answer

One problem with your trigger is that it is potentially updating all rows in the table, even if only one row was updated or inserted. If someone accidentally sets the values to NULL, they'll then get updated to the current time, the next time the trigger runs. Does this make sense for your application? I would think it makes more sense to leave past values alone (deal with those separately, though it seems doubtful any still exist), and only bother updating rows that are currently impacted directly by the trigger. You do that by joining to the inserted pseudo-table:

UPDATE sr SET saledate = GETDATE()
  FROM dbo.salerecords AS sr
  INNER JOIN inserted AS i
  ON sr.key_column = i.key_column -- you'll need to update this
  WHERE sr.saledate IS NULL;

That said, I agree with @SoleDBAGuy, who suggested a default constraint. Here is how you could implement that:

ALTER TABLE dbo.salerecords
  ADD CONSTRAINT df_saledate DEFAULT (GETDATE()) FOR saledate;
GO
ALTER TABLE dbo.salerecords
  ALTER COLUMN df_saledate datetime NOT NULL;

And then drop the trigger. Note that the second command may fail; if you have null values in there already, it's hard to justify just giving them "right now" as their sale date, when they could potentially be years old. So you can look at those individually, or just apply some date to them all, like:

UPDATE dbo.salerecords SET saledate = GETDATE();
-- or
UPDATE dbo.salerecords SET saledate = '19000101'; -- beware magic number

Finally, please always use the schema prefix.

Related Solutions

Mysql – How to structure IF condition in MySQL trigger

I assume you will value TableB first as it contains the order_no. In that case you need to use an update statement in your trigger instead of an insert statement:

SQL Fiddle

MySQL 5.6.6 m9 Schema Setup:

CREATE TABLE TableA(order_id INT, sku VARCHAR(10));

CREATE TABLE TableB(order_id INT, order_no VARCHAR(10),sku_copy VARCHAR(10));

GO
CREATE TRIGGER trigger_name
    AFTER INSERT ON TableA
    FOR EACH ROW BEGIN

    UPDATE TableB
    SET sku_copy = NEW.sku
    WHERE order_id = NEW.order_id;
END;
GO
INSERT INTO TableB(order_id, order_no)VALUES(1,'111');
INSERT INTO TableB(order_id, order_no)VALUES(2,'222');
INSERT INTO TableB(order_id, order_no)VALUES(3,'333');
GO
INSERT INTO TableA(order_id, sku)VALUES(1,'AAA'),(2,'BBB');

(The GO in this example is used as a batch separator and not send to MySQL.)

Query 1:

SELECT * FROM TableB;

Results:

| ORDER_ID | ORDER_NO | SKU_COPY |
----------------------------------
|        1 |      111 |      AAA |
|        2 |      222 |      BBB |
|        3 |      333 |   (null) |

If you also want to react to updates, just create an AFTER UPDATE trigger like this:

SQL Fiddle

MySQL 5.6.6 m9 Schema Setup:

CREATE TABLE TableA(order_id INT, sku VARCHAR(10));

CREATE TABLE TableB(order_id INT, order_no VARCHAR(10),sku_copy VARCHAR(10));

GO
CREATE TRIGGER TableA_AfterInsert
    AFTER INSERT ON TableA
    FOR EACH ROW BEGIN

    UPDATE TableB
    SET sku_copy = NEW.sku
    WHERE order_id = NEW.order_id;
END;
GO
INSERT INTO TableB(order_id, order_no)VALUES(1,'111');
INSERT INTO TableB(order_id, order_no)VALUES(2,'222');
INSERT INTO TableB(order_id, order_no)VALUES(3,'333');
GO
INSERT INTO TableA(order_id, sku)VALUES(1,'AAA'),(2,'BBB');
GO
-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
GO
CREATE TRIGGER TableA_AfterUpdate
    AFTER UPDATE ON TableA
    FOR EACH ROW BEGIN

    IF (OLD.sku != NEW.sku)
    THEN
      UPDATE TableB
      SET sku_copy = NEW.sku
      WHERE order_id = NEW.order_id;
    END IF;
END;
GO
UPDATE TableA
  SET sku = 'NEW'
WHERE order_id = 2;
GO

Query 1:

SELECT * FROM TableB;

Results:

| ORDER_ID | ORDER_NO | SKU_COPY |
----------------------------------
|        1 |      111 |      AAA |
|        2 |      222 |      NEW |
|        3 |      333 |   (null) |

In both cases the NEW and OLD virtual tables refer to the table the trigger is defined on. NEW contains the new version of the row that was inserted or changed. OLD contains the pre-change version of the row. OLD is only defined in an update trigger as there is no old version on an insert.

Sql-server – Trigger to update a date field on one table when another table is updated

You should be using the inserted and deleted pseudo tables to find out the rows for which the column was affected by the trigger - and then update only the related rows in the second table:

CREATE TRIGGER trg_LastSaleDate ON dbo.Transheaders
    AFTER UPDATE
AS
    IF UPDATE(TradingDate)
    BEGIN
        UPDATE c
            SET ZLastSale = i.TradingDate
        FROM dbo.Customers AS c
          JOIN inserted AS i
            ON i.CustomerID = c.CustomerID     -- use the appropriate column for joining
          JOIN deleted AS d
            ON  i.TransheadersID = d.TransheadersID
            AND ( i.TradingDate <> d.TradingDate
               OR d.TradingDate IS NULL
                ) ;
    END ;

Best Answer

Related Solutions

Mysql – How to structure IF condition in MySQL trigger

Sql-server – Trigger to update a date field on one table when another table is updated

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