I tried to create below Trigger but I have an Error.
Can I Use Update or use 'case when' in trigger?
Please help me to fix my issue here.
Code Explanation:
I want to update my existing row after insert or update.
Do not change the 'FUSDate1' or 'FUSDate2' If I didn't add anything to the 'FUSDate1' or 'FUSDate2'
Update the FUSDate to the New One or Inserted one If I Updated or inserted data to FUSDate
Code:
delimiter //
create trigger SafetyCertificationTRG
after insert on SafetyCertification
for each row
begin
case when (FUSDate1='' or FUZDate1 is NULL) then (FUZDate1=OLD.FUSDate1) else (update SafetyCertification set FUZDate1=NEW.FUSDate1) end;
case when (FUSDate2='' or FUZDate2 is NULL) then (FUZDate2=NEW.FUSDate2) else (update SafetyCertification set FUZDate2=NEW.FUSDate2) end;
end //
delimiter ;
Edit: I am going to add some information here to make the question more clear.
I have one column as FUS that can be get these 3 values only:('FUS1', 'FUS2' and 'FUS3')
I have 3 other columns: FUSDate1, FUSDate2, FUSDate3.
I want to save the Current Date to The FUSDate1 Or FUSDate2 Or FUSDate3 based on the user User Selection of FUS. (They are in same Table)
I used the provided answer and change it to this but I cannot do the above.
Code: This code is just for FUS1 and FUSDate1
delimiter //
CREATE TRIGGER SafetyCertification_bu
BEFORE UPDATE ON SafetyCertification
FOR EACH ROW
BEGIN
-- detect a change made to a value in col
IF OLD.FUS <=> NEW.FUS THEN
-- value of col is not changed, so do nothing
DO 0;
ELSE
-- we detected a new value was assigned to col
IF OLD.FUS ='%FUS1%' THEN
-- we can override the new value, keep it the same
SET NEW.FUSDate1 = CURDATE();
END IF;
END IF;
END //
delimiter ;
Another code that I expected to do my work but still have problem, Does not update Like above Code:
delimiter //
CREATE TRIGGER SafetyCertification_bu
BEFORE INSERT ON SafetyCertification
FOR EACH ROW
BEGIN
IF NEW.FUS='%FUS1%' THEN
SET new.FUSDate1=MD5(CURDATE());
END IF;
END //
delimiter ;
Update 3:
The Third code that provided in answer does not add anything to the FUSdate1 and 2 and 3 when i update or insert any data.
Code
DELIMITER $$
CREATE TRIGGER SafetyCertification_bu
BEFORE UPDATE ON SafetyCertification
FOR EACH ROW
BEGIN
-- set one of the `fusdateN` columns to current date
-- which column to set depends on the value assigned to `fus`
IF NEW.fus = 'FUS1' THEN
SET NEW.fusdate1 = DATE(NOW());
ELSEIF NEW.fus = 'FUS2' THEN
SET NEW.fusdate2 = DATE(NOW());
ELSEIF NEW.fus = 'FUS3' THEN
SET NEW.fusdate3 = DATE(NOW());
END IF;
END$$
DELIMITER ;
A couple of notes:
A trigger cannot issue an UPDATE against the table that fired the trigger, this is prohibited.
The unqualified references (e.g. FUSDate1 and FUZDate1) are not valid. Those references don't resolve to anything.
The reference to OLD.FUSDate1 is invalid in the context of an AFTER INSERT trigger. In an UPDATE trigger, the OLD.col refers to the value of col before the update.
The expression (FUZDate1=OLD.FUSDate1) is not an assignment, it's a comparison that's going to return 0, 1 or NULL.
If we want to trigger on an UPDATE and an INSERT, that will require two separate triggers.
If we want to modify the contents of the current row, we can use BEFORE trigger instead of AFTER.
I want to update my existing row after insert or update.
It would be much easier to apply changes before the row is inserted or updated. We can assign a value to a column col by referencing NEW.col in an assignment in a BEFORE INSERT or BEFORE UPDATE trigger. For example:
SET NEW.col = expr;
Do not change the FUSDate1 or FUSDate2 If I didn't add anything to the FUSDate1 or FUSDate2
This seems pretty straightforward. Just don't make any assignments to NEW.FUSDate1 or NEW.FUSDate2.
Update the FUSDate to the New One or Inserted one If I Updated or inserted data to FUSDate
The example proposed trigger contains references to FUZDate1 or FUZDate2, but there's no mention of these columns in the specification. The specification is confusing.
An UPDATE statement will assign a value to a column, no need for a trigger to do that. An INSERT statement can assign a value to a column, again, no need for a trigger for that.
The specification is not clear. Providing example starting state (rows in the table), and example INSERT or UPDATE statements, and the desired state after the statement is executed would go a long ways towards clarifying the requirements.
A demonstration of a BEFORE UPDATE trigger that prevents a new value being assigned to a particular column:
DELIMITER $$
CREATE TRIGGER SafetyCertification_bu
BEFORE UPDATE ON SafetyCertification
FOR EACH ROW
BEGIN
-- detect a change made to a value in col
IF OLD.col <=> NEW.col THEN
-- value of col is not changed, so do nothing
DO 0;
ELSE
-- we detected a new value was assigned to col
IF OLD.col IS NOT NULL THEN
-- we can override the new value, keep it the same
SET NEW.col = OLD.col;
END IF;
END IF;
END$$
DELIMITER ;
For what this example trigger achieves, we don't necessarily need that many IF conditions; those are included as a demonstrate some of the checks we can perform, how we can make references to the existing value of col and the new value assigned to col.
FOLLOWUP
Based on the update information in the question, here's an example of a BEFORE UPDATE trigger that satisfies the specification.
This is for the UPDATE action. To get this same behavior with an INSERT statement, this trigger definition needs to be repeated, with BEFORE INSERT in place of BEFORE UPDATE.
(I would use the name _bu for the before update trigger, and _bi for before insert trigger.)
DELIMITER $$
CREATE TRIGGER SafetyCertification_bu
BEFORE UPDATE ON SafetyCertification
FOR EACH ROW
BEGIN
-- set one of the `fusdateN` columns to current date
-- which column to set depends on the value assigned to `fus`
IF NEW.fus = 'FUS1' THEN
SET NEW.fusdate1 = DATE(NOW());
ELSEIF NEW.fus = 'FUS2' THEN
SET NEW.fusdate2 = DATE(NOW());
ELSEIF NEW.fus = 'FUS3' THEN
SET NEW.fusdate3 = DATE(NOW());
END IF;
END$$
DELIMITER ;
second followup
To answer the question about using CASE WHEN statement in the context of a MySQL stored program...
We could implement the example trigger (directly above in this answer) replacing the IF-THEM with either of the two forms of the CASE statement.
either
CASE
WHEN NEW.fus = 'FUS1' THEN
SET NEW.fusdate1 = DATE(NOW());
WHEN NEW.fus = 'FUS2' THEN
SET NEW.fusdate2 = DATE(NOW());
WHEN NEW.fus = 'FUS3' THEN
SET NEW.fusdate3 = DATE(NOW());
END CASE;
-or-
CASE NEW.fus
WHEN 'FUS1' THEN
SET NEW.fusdate1 = DATE(NOW());
WHEN 'FUS2' THEN
SET NEW.fusdate2 = DATE(NOW());
WHEN 'FUS3' THEN
SET NEW.fusdate3 = DATE(NOW());
END CASE;
note
The CASE statement is available in MySQL stored programs; outside of a stored program, it is not a valid SQL statement.
Also, we should not confuse this CASE statement with the CASE expression. The CASE expression is valid in the context of a SQL statement, such as a SELECT or UPDATE statement.
DEMONSTRATION
"I examined the Trigger, But unfortunately does not save anything in fusDates."
#Christiano: here is a simple demonstration
create table
CREATE TABLE `safety_certification`
( id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY
, fus VARCHAR(5)
, fusdate1 DATE
, fusdate2 DATE
, fusdate3 DATE
) ENGINE=INNODB
;
populate table with demonstration rows
INSERT INTO `safety_certification` (id, fus, fusdate1, fusdate2, fusdate3) VALUES
( 1, '', NULL, NULL, NULL)
,( 2, '', NULL, NULL, NULL)
,( 3, '', NULL, NULL, NULL)
,( 4, '', NULL, NULL, NULL)
,( 5, '', NULL, NULL, NULL)
;
create trigger
DELIMITER $$
CREATE TRIGGER `safety_certification_bu`
BEFORE UPDATE ON `safety_certification`
FOR EACH ROW
BEGIN
-- set one of the `fusdateN` columns to current date
-- which column to set depends on the value assigned to `fus`
IF NEW.fus = 'FUS1' THEN
SET NEW.fusdate1 = DATE(NOW());
ELSEIF NEW.fus = 'FUS2' THEN
SET NEW.fusdate2 = DATE(NOW());
ELSEIF NEW.fus = 'FUS3' THEN
SET NEW.fusdate3 = DATE(NOW());
END IF;
END$$
DELIMITER ;
updates will exercise BEFORE UPDATE trigger we just defined
UPDATE `safety_certification` sc SET sc.fus = 'FUS1' WHERE sc.id = 1 ;
UPDATE `safety_certification` sc SET sc.fus = 'FUS2' WHERE sc.id = 2 ;
UPDATE `safety_certification` sc SET sc.fus = 'FUS3' WHERE sc.id = 3 ;
UPDATE `safety_certification` sc SET sc.fus = 'FUS4' WHERE sc.id = 4 ;
display contents of table
SELECT * FROM `safety_certification`;
returns:
id fus fusdate1 fusdate2 fusdate3
------ ------ ---------- ---------- ------------
1 FUS1 2018-05-04 (NULL) (NULL)
2 FUS2 (NULL) 2018-05-04 (NULL)
3 FUS3 (NULL) (NULL) 2018-05-04
4 FUS4 (NULL) (NULL) (NULL)
5 (NULL) (NULL) (NULL)
seems like the trigger is populating the columns fusdate1, fusdate2 and fusdate3 per the specification, when some particular values are assigned to fus
I had a same problem and I used two trigger,
First trigger send data to the other table, so now you can create another trigger to send this data to the first table. I think it is low performance but it is the only way that I reached to it. I hope others have another solution for u.
i'm trying to update 2 column with trigger before insert, but i have unexpected result. i insert some data and the 2 last column will automatically inserted with values, here my first attempt
see? the last 2 column is null even i set some trigger and function to fill that columns automatically. Here my second attempt WITH EXACTLY SAME DATA
the last 2 column is filled with data, but i don't understand why the first attempt is fail?
here my trigger i use in the column total_harga
CREATE TRIGGER `set_total_harga` BEFORE INSERT ON `tbl_transaksi_detail`
FOR EACH ROW BEGIN
set NEW.total_harga = hitungTotalHargaPerItem(NEW.qty, NEW.harga_satuan);
END
trigger for column harga_satuan
CREATE TRIGGER `set_harga_satuan` BEFORE INSERT ON `tbl_transaksi_detail`
FOR EACH ROW BEGIN
set NEW.harga_satuan = set_Harga_Unit(NEW.unit, NEW.id_barang, NEW.no_transaksi);
END
function set_Harga_Unit
BEGIN
DECLARE
q,
id_toko INT;
SET
id_toko =(
SELECT DISTINCT
`tbl_transaksi`.`id_toko`
FROM
`tbl_transaksi`,
`tbl_transaksi_detail`
WHERE
`tbl_transaksi`.`no_transaksi` = no_trans
); IF unit = "PCS" THEN
SET
q =(
SELECT
`tbl_harga_jual`.`harga_pcs`
FROM
`tbl_harga_jual`
WHERE
`tbl_harga_jual`.`id_barang` = id_brg AND `tbl_harga_jual`.`id_toko` = id_toko
); RETURN q; ELSEIF unit = "PAK" THEN
SET
q =(
SELECT
`tbl_harga_jual`.`harga_pak`
FROM
`tbl_harga_jual`
WHERE
`tbl_harga_jual`.`id_barang` = id_brg AND `tbl_harga_jual`.`id_toko` = id_toko
); RETURN q; ELSEIF unit = "KARTON" THEN
SET
q =(
SELECT
`tbl_harga_jual`.`harga_karton`
FROM
`tbl_harga_jual`
WHERE
`tbl_harga_jual`.`id_barang` = id_brg AND `tbl_harga_jual`.`id_toko` = id_toko
); RETURN q;
END IF; RETURN q;
END
function hitungTotalHargaPerItem
BEGIN
DECLARE hasil int;
set hasil = qty * harga_satuan;
RETURN hasil;
END
The root cause serms to be the select that sets id_toko variable's value:
SET
id_toko =(
SELECT DISTINCT
`tbl_transaksi`.`id_toko`
FROM
`tbl_transaksi`,
`tbl_transaksi_detail`
WHERE
`tbl_transaksi`.`no_transaksi` = no_trans
);
In the select you inner join tbl_transaksi_detail (the table with the trigger in question) on another table. However, in the 1st case tbl_transaksi_detail is still empty (the trigger is before insert), therefore id_toko variable is set to null.
This will result q being null, which in turn results in the entire calculation set to null.
In the 2nd case there is already a record inserted into tbl_transaksi_detail table, therefore the calculation returns a non null value. But it returns the correct values only because the 1st and 2nd records' details are exactly the same.
I do not really understand that select that calculates id_toko anyway. If that is a transaction id, then you may use last_insert_id() if it is auto increment and the transaction record has just been created or max(id_toko) to get the highest value of id_toko (this is not multi user safe).
it seem i have mistaken select query in function set_Harga_Unit, based on clues from #Shadow
SET
id_toko =(
SELECT DISTINCT
`tbl_transaksi`.`id_toko`
FROM
`tbl_transaksi`,
`tbl_transaksi_detail`<<== I DON'T NEED THIS
WHERE
`tbl_transaksi`.`no_transaksi` = no_trans
); IF unit = "PCS" THEN
when first insert in tbl_transaksi_detail, the value no_transaksi is null because i use trigger before insert in empty table (tbl_transaksi_detail), so i remove tbl_transaksi_detail from query
SET
id_toko =(
SELECT DISTINCT
`tbl_transaksi`.`id_toko`
FROM
`tbl_transaksi`
WHERE
`tbl_transaksi`.`no_transaksi` = no_trans
); IF unit = "PCS" THEN
now it working, thanks everybody!
So let's say i have a table that has a column "id_author" , i'd like to set a limit for the occurrence of the same value ; example : can't have more than 3 same "id_author" values so when i insert the 4th one it's refused.
Is there a way to implement this? Thanks
You can use a trigger before insert, that will throw a signal in case it violates your condition:
CREATE TRIGGER tooManyRecords
BEFORE INSERT ON yourTable
FOR EACH ROW
BEGIN
DECLARE counter INTEGER;
SELECT COUNT(*) INTO counter FROM yourTable
WHERE id_author = NEW.id_author;
IF counter >= 3 THEN
SIGNAL SQLSTATE '45000' SET message_text = 'there are already 3 records for the provided id';
END
I've been trying to solve this problem. Here is the code:
CREATE TRIGGER some_trigger AFTER UPDATE ON table_a
FOR EACH ROW BEGIN
DECLARE tname VARCHAR(20);
IF (table_a.field_offer=1) THEN
SET tname='table_b';
ELSEIF (table_a.field_offer=0) THEN
SET tname='table_c';
END IF;
IF ((new.field_state = 0)) THEN
UPDATE tname join table_a on tname.ID=table_a.ref_field
SET tname.STOCK = tname.STOCK -1;
ELSEIF ((new.field_state = 1)) THEN
UPDATE tname join table_a on tname.ID=table_a.ref_field
SET tname.STOCK = tname.STOCK +1;
END IF;
END;
I am getting:
Unknown table 'table_a' in field list. Field_offer and field_state can
be null.
I've shown below what was said in the comments to the question:
CREATE TRIGGER some_trigger AFTER UPDATE ON table_a
FOR EACH ROW BEGIN
DECLARE tname VARCHAR(20);
IF (NEW.field_offer=1) THEN
UPDATE `table_b`
SET STOCK = CASE NEW.field_state
WHEN 0 THEN STOCK - 1
WHEN 1 THEN STOCK + 1
ELSE STOCK
END
WHERE ID=NEW.ref_field
;
ELSEIF (NEW.field_offer=0) THEN
UPDATE `table_c`
SET STOCK = CASE NEW.field_state
WHEN 0 THEN STOCK - 1
WHEN 1 THEN STOCK + 1
ELSE STOCK
END
WHERE ID=NEW.ref_field
;
END IF;
...
Note that I changed the updates from UPDATE ... JOIN as MySQL does not allow you to change the data of the triggered table; while you were not actually updating table_a, the JOIN could have been enough for MySQL to have objected... that and the joins would've updated every row in table_b/c that had a match in table_a, not just table_a rows related to the values in or row of the trigger.
I have a table which contains two columns
1.Clanid
2.Active
My problem is that i dont want any value in Clanid column to be inserted in this table if this value is already in Clanid column and Active for that value is 1.
For example
Clanid Active
1 1
2 1
3 0
Now it should not be possible to insert a record with Clanid=1 and Active=1 but i can insert Clanid=3 and Active=1 as this record is not there.
Try this:
delimiter //
create trigger unique_clanid
before insert on mytable
for each row
begin
if new.active and exists (
select * from mytable
where clanid = new.clanid
and active) then
signal sqlstate '02000' set MESSAGE_TEXT = 'Duplicate ClanID';
end if;
end//
delimiter ;
I think you should handle in your app level, but you want to handle in DB lavel, you can write trigger check it
you can check count record ( where Clanid = #param and Active =1)
if count > 1 : rollback
I am not available mysql to test , i just can describe my solution as following ( i;m not sure the syntax correct, it is too long time i don't write trigger in mysql)
CREATE TRIGGER test BEFORE INSERT ON table_name
FOR EACH ROW
BEGIN
DECLARE newClanId integer;
DECLARE counts integer;
Set #newClanId = NEW.Clanid;
Set #count := (SELECT count (*) FROM table_name
WHERE Clanid = #newClanId and Active =1)
IF #count > 1 THEN ROLLBACK;
END;