I am having trouble with updating 2 tables with one trigger, its giving me an error near "New.userid"
CREATE TRIGGER userDownloads AFTER INSERT ON Downloads
FOR EACH ROW
UPDATE Project SET PROJECT_DOWNLOADS = PROJECT_DOWNLOADS + 1 WHERE PROJECTID = NEW.ProjectID,
UPDATE User SET NO_OF_DOWNLOADS = NO_OF_DOWNLOADS + 1 WHERE USERID = NEW.UserID;
You have to write your trigger this way:
DELIMITER //
CREATE TRIGGER userDownloads AFTER INSERT ON Downloads
FOR EACH ROW
BEGIN
UPDATE Project SET PROJECT_DOWNLOADS = PROJECT_DOWNLOADS + 1 WHERE PROJECTID = NEW.ProjectID;
UPDATE User SET NO_OF_DOWNLOADS = NO_OF_DOWNLOADS + 1 WHERE USERID = NEW.UserID;
END//
Please see it working here.
But are you sure you need a trigger? Why don't you just do a COUNT on your Downloads table?
SELECT ProjectID, COUNT(*) AS PROJECT_DOWNLOADS
FROM Downloads
GROUP BY ProjectID;
SELECT UserID, COUNT(*) AS NO_OF_DOWNLOADS
FROM Downloads
GROUP BY UserID;
Related
I'm trying to create a trigger in phpmyadmin and I have 2 tables, Items and Inventory. This is for a Library Database. When i insert a new item, if the items isbn already exists in the inventory, i want to add to the totalCopies of that item in the inventory. If not, i want it to insert into inventory a new row with the new items isbn. This is my first time using triggers and I'm getting syntax errors. This is what i have right now.
BEGIN
IF ((SELECT COUNT(*) FROM inventory WHERE inventory.isbn = NEW.isbn) > 0) THEN
(
UPDATE inventory
SET inventory.totalCopies = inventory.totalCopies + 1
WHERE inventory.isbn = NEW.isbn
SET inventory.totalAvailable = inventory.totalAvailable + 1
WHERE inventory.isbn = NEW.isbn
)
ELSE
INSERT INTO inventory VALUES( , NEW.isbn, 1, 1, 0)
END
The inventory columns are : inventoryID (PrimaryKey)(autoincrement), isbn, totalCopies, totalAvailable, totalCheckedOut.
I assume for this trigger that inventory id is an auto_increment value,
or else the insert gives an error.
the UPDATE query can be a little simplifoed
DELIMITER $$
CREATE TRIGGER insorup
AFTER INSERT
ON ORDERS FOR EACH ROW
BEGIN
IF (EXISTS(SELECT 1 FROM inventory WHERE inventory.isbn = NEW.isbn) ) THEN
UPDATE inventory
SET inventory.totalCopies = inventory.totalCopies + 1 ,
inventory.totalAvailable = inventory.totalAvailable + 1
WHERE inventory.isbn = NEW.isbn;
ELSE
INSERT INTO inventory VALUES ( NEW.isbn, 1, 1, 0);
END IF;
END$$
DELIMITER ;
as you see in the comment, Shadow pointed out that it is also possible to reduce the inner Part. When you have the column ISBN declared as UNIQUE
DELIMITER $$
CREATE TRIGGER insorup
AFTER INSERT
ON ORDERS FOR EACH ROW
BEGIN
INSERT INTO
inventory VALUES ( NEW.isbn, 1, 1, 0)
ON DUPLICATE KEY UPDATE inventory.totalCopies = inventory.totalCopies + 1 ,
inventory.totalAvailable = inventory.totalAvailable + 1;
END$$
DELIMITER ;
I have a table like this
tbl_user
id
user_id
amount
first i want to update a row based on id
$amount = 123; // dyanamic value
$sql = "UPDATE tbl_user SET amount=amount-'$amount' WHERE id='$id' LIMIT 1 ";
now i want to get updated value of amount column i have applied this sql
$sql = "SELECT amount FROM tbl_user WHERE id='$id' LIMIT 1 ";
my question is can i combine both of above sql or any single query to achieve above task?
The best you could imitate is to use two lines of queries, probably using a variable like:
UPDATE tbl_user SET
amount = #amount := amount-'$amount'
WHERE id='$id' LIMIT 1;
SELECT #amount;
The best you could do then is to create a Stored Procedure like:
DELIMITER //
CREATE PROCEDURE `return_amount` ()
BEGIN
UPDATE tbl_user SET
amount = #amount := amount-'$amount'
WHERE id='$id' LIMIT 1;
SELECT #amount;
END //
And then call Stored Procedure in your PHP.
Note: PostgreSQL has this kind of option using RETURNING statement that would look like this:
UPDATE tbl_user SET amount=amount-'$amount'
WHERE id='$id' LIMIT 1
RETURNING amount
See here
A function can do this easily. It sounds like you want to limit how many times your code connects to the database. With a stored function or procedure, you are only making one connection. Yes, the stored function has two queries inside it (update then select), but these are executed on the server side without stopping to do round trips to the client.
http://sqlfiddle.com/#!2/0e6a09/1/0
Here's my skeleton of your table:
CREATE TABLE tbl_user (
id VARCHAR(100) PRIMARY KEY,
user_id VARCHAR(100),
amount DECIMAL(17,4) );
INSERT INTO tbl_user VALUES ('1', 'John', '100.00');
And the proposed function:
CREATE FUNCTION incrementAmount
(p_id VARCHAR(100), p_amount DECIMAL(17,4))
RETURNS DECIMAL(17,4)
BEGIN
UPDATE tbl_user
SET amount = amount + p_amount
WHERE id = p_id;
RETURN (SELECT amount FROM tbl_user WHERE id = p_id);
END
//
Then you just run one query, a SELECT on the function you just created:
SELECT incrementAmount('1', 5.00)
The query result is:
105
It is not possible with a single query, but you can combine multiple commands into a script and execute them with a single request to the database server.
Run this script:
"UPDATE tbl_user SET amount=amount-'$amount' WHERE id='".$id."';SELECT amount FROM tbl_user WHERE id='".$id."'; "
Also, you might want to check whether $id is a number, as I do not see a protection against SQL injection inside your code. SQL injection is a serious threat, you would do better to prepare and protect yourself against it.
We can also use:
UPDATE tbl_user SET id = LAST_INSERT_ID(id), amount = 2.4,user_id=4 WHERE id = 123;
// SELECT
$id =SELECT LAST_INSERT_ID();
SELECT amount,user_id FROM tbl_user WHERE id = $id LIMIT 1
Here would be the procedure
CREATE PROCEDURE UpdateAndSelect
(
#amount MONEY,
#id INT
)
AS
BEGIN
UPDATE tbl_user
SET amount = #amount
WHERE id = #id
LIMIT 1
SELECT amount
FROM tbl_user
WHERE id = #id
LIMIT 1
END
GO
You would call this stored procedure by setting your variables (#amoutn and #id) and then calling:
exec UpdateAndSelect
Hope this helps solve your problem
I have the following schema : SQL Fiddle.
The trigger is updating the articles.votes field. I also need it to update the members.points field and the members lifetime_points fields with the same formula as updates the articles.votes field. How do I do that?
Are you looking for this?
DELIMITER $$
CREATE TRIGGER tg_ai_article_votes
AFTER INSERT ON article_votes
FOR EACH ROW
BEGIN
UPDATE articles
SET votes = COALESCE(votes, 0) + 1
WHERE id = NEW.article_id;
UPDATE members
SET points = COALESCE(points, 0) + 1,
lifetime_points = COALESCE(lifetime_points, 0) + 1
WHERE id = NEW.member_id;
END$$
CREATE TRIGGER tg_ad_article_votes
AFTER DELETE ON article_votes
FOR EACH ROW
BEGIN
UPDATE articles
SET votes = COALESCE(votes, 0) - 1
WHERE id = OLD.article_id;
UPDATE members
SET points = COALESCE(points, 0) - 1,
lifetime_points = COALESCE(lifetime_points, 0) - 1
WHERE id = OLD.member_id;
END$$
DELIMITER ;
Here is SQLFiddle demo
I have a table where there is some duplicate file access information where a duplicate file access is defined as the same user accessing the same file back to back. In other words, if the user accesses file A,B,A in that order, it's NOT considered a duplicate. So basically, per user I want to make sure that every subsequent access is for a file different from the last one.
UserID FileID
1 1
2 1
1 1 <- Remove
2 1 <- Remove
2 2
1 2
2 2 <- Remove
1 1
1 2
Anyone know how to approach something like this in mysql? Ideally, I would like to use it without the use of a function but I'm open to a function if it's the only option.
The table has the following columns: ID (primary key), userID, fileID, accessTime
If you made a SPROC it would look something like this. You may need another temp table and loop as the DELETE statement may fail while the cursor is open.
CREATE PROCEDURE `proc_CURSOR` ()
BEGIN
CREATE TEMPORARY TABLE lastUserAccess;
DECLARE cur1 CURSOR FOR SELECT userId, fileId, pkId FROM table1 ORDER BY time_stamp;
DECLARE a, b, c, d INT;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET a = 1;
OPEN cur1;
WHILE a = 0 DO
FETCH cur1 INTO b, c, d;
SELECT fileId FROM lastUserAccess WHERE userId = b
IF fileId IS NULL THEN
INSERT INTO lastUserAccess (b, c, d);
ELSE
IF fileId = c THEN
DELETE FROM table1 WHERE pkId = d;
ELSE
UPDATE lastUserAccess SET fileId = c WHERE userId = b;
END IF;
END IF;
END WHILE;
CLOSE cur1;
END
For mysql
DELETE a from tbl a , tbl b WHERE a.Id>b.Id and
a.UserID = b.UserID and a.FileID= b.FileID;
Check this fiddle http://sqlfiddle.com/#!2/aece0a/1
Wont work in mysql, for sql server
DELETE FROM tbl WHERE ID NOT IN (SELECT MIN(ID)
FROM tbl GROUP BY userID, fileID)
Hope this works for you.
I have a table which contains relative large data,
so that it takes too long for the statements below:
SELECT MIN(column) FROM table WHERE ...
SELECT MAX(column) FROM table WHERE ...
I tried index the column, but the performance still does not suffice my need.
I also thought of caching min and max value in another table by using trigger or event.
But my MySQL version is 5.0.51a which requires SUPER privilege for trigger and does not support event.
It is IMPOSSIBLE for me to have SUPER privilege or to upgrade MySQL.
(If possible, then no need to ask!)
How to solve this problem just inside MySQL?
That is, without the help of OS.
If your column is indexed, you should find min(column) near instantly, because that is the first value MySQL will find.
Same goes for max(column) on an indexed column.
If you cannot add an index for some reason the following triggers will cache the MIN and MAX value in a separate table.
Note that TRUE = 1 and FALSE = 0.
DELIMITER $$
CREATE TRIGGER ai_table1_each AFTER INSERT ON table1 FOR EACH ROW
BEGIN
UPDATE db_info i
SET i.minimum = LEAST(i.minimum, NEW.col)
,i.maximum = GREATEST(i.maximum, NEW.col)
,i.min_count = (i.min_count * (new.col < i.minumum))
+ (i.minimum = new.col) + (i.minimum < new.col)
,i.max_count = (i.max_count * (new.col > i.maximum))
+ (i.maximum = new.col) + (new.col > i.maximum)
WHERE i.tablename = 'table1';
END $$
CREATE TRIGGER ad_table1_each AFTER DELETE ON table1 FOR EACH ROW
BEGIN
DECLARE new_min_count INTEGER;
DECLARE new_max_count INTEGER;
UPDATE db_info i
SET i.min_count = i.min_count - (i.minimum = old.col)
,i.max_count = i.max_count - (i.maximum = old.col)
WHERE i.tablename = 'table1';
SELECT i.min_count INTO new_min_count, i.max_count INTO new_max_count
FROM db_info i
WHERE i.tablename = 'table1';
IF new_max_count = 0 THEN
UPDATE db_info i
CROSS JOIN (SELECT MAX(col) as new_max FROM table1) m
SET i.max_count = 1
,i.maximum = m.new_max;
END IF;
IF new_min_count = 0 THEN
UPDATE db_info i
CROSS JOIN (SELECT MIN(col) as new_min FROM table1) m
SET i.min_count = 1
,i.minimum = m.new_min;
END IF;
END $$
DELIMITER ;
The after update trigger will be some mix of the insert and delete triggers.