When I create one trigger of before insert for prevent wrong input then trigger has created but after insert values in that table then it create error like Error-1054 Unknown column 'column-name' in 'field-list'. I want to create trigger for prevent wrong input from users then how is it possible that insert values in table after creating trigger. Code shown as below of trigger
CREATE DEFINER=`root`#`localhost` TRIGGER `mobile_no` BEFORE INSERT ON `invoiceform_clients` FOR EACH ROW
BEGIN
if length(clientPhonenumber)=10 THEN
insert into invoiceform_clients(clientPhonenumber) values(clientPhonenumber);
ELSE
SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT= 'Mobile NO. must be in 10 digit';
end if;
END;
You don't need to repeat the insert statement inside the trigger body - just validate the column value and throw the signal if it's wrong. If the trigger code exits normally, the original INSERT which fired the trigger will succeed as well.
You should also be testing NEW.clientPhonenumber instead of just clientPhonenumber - this specifies that you want to check the field in the record as it will exist after the INSERT completes.
The trigger should look something like this:
CREATE DEFINER=`root`#`localhost` TRIGGER `mobile_no`
BEFORE INSERT ON `invoiceform_clients`
FOR EACH ROW
BEGIN
IF length(NEW.clientPhonenumber) != 10 THEN
SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT= 'Mobile NO. must be in 10 digit';
END IF;
END;
Related
im trying to create trigger that prevent insert on buku_dalam_pinjam with certain condition from other table which is anggota_dosen. this is my current trigger
CREATE DEFINER=`root`#`localhost` TRIGGER `buku_dalam_pinjam_BI`
BEFORE INSERT ON `buku_dalam_pinjam`
FOR EACH ROW BEGIN
if (buku_dalam_pinjam.id_agt_dosen=anggota_dosen.id_agt_dosen and
anggota_dosen.ttl_proses_pinjam >=5) then
signal sqlstate '45000' set message_text="error message";
end if;
END
it was succesfully created, then when i try to insert data on buku_dalam_pinjam
it gave me error message, but when i erase the trigger it let me insert on buku_dalam_pinjam table. so is there any mistake in my trigger?
anggota_dosen table
buku_dalam_pinjam table
error message when i include the trigger
try this
drop trigger if exists buku_dalam_pinjam_BI;
delimiter $$
CREATE TRIGGER `buku_dalam_pinjam_BI`
BEFORE INSERT ON buku_dalam_pinjam
FOR EACH ROW BEGIN
if exists (select 1 from anggota_dosen
where new.id_agt_dosen = anggota_dosen.id_agt_dosen and
anggota_dosen.ttl_proses_pinjam >=5) then
signal sqlstate '45000' set message_text="error message";
end if;
END $$
delimiter ;
If I have a trigger before the update on a table, how can I throw an error that prevents the update on that table?
As of MySQL 5.5, you can use the SIGNAL syntax to throw an exception:
signal sqlstate '45000' set message_text = 'My Error Message';
State 45000 is a generic state representing "unhandled user-defined exception".
Here is a more complete example of the approach:
delimiter //
use test//
create table trigger_test
(
id int not null
)//
drop trigger if exists trg_trigger_test_ins //
create trigger trg_trigger_test_ins before insert on trigger_test
for each row
begin
declare msg varchar(128);
if new.id < 0 then
set msg = concat('MyTriggerError: Trying to insert a negative value in trigger_test: ', cast(new.id as char));
signal sqlstate '45000' set message_text = msg;
end if;
end
//
delimiter ;
-- run the following as seperate statements:
insert into trigger_test values (1), (-1), (2); -- everything fails as one row is bad
select * from trigger_test;
insert into trigger_test values (1); -- succeeds as expected
insert into trigger_test values (-1); -- fails as expected
select * from trigger_test;
Here is one hack that may work. It isn't clean, but it looks like it might work:
Essentially, you just try to update a column that doesn't exist.
Unfortunately, the answer provided by #RuiDC does not work in MySQL versions prior to 5.5 because there is no implementation of SIGNAL for stored procedures.
The solution I've found is to simulate a signal throwing a table_name doesn't exist error, pushing a customized error message into the table_name.
The hack could be implemented using triggers or using a stored procedure. I describe both options below following the example used by #RuiDC.
Using triggers
DELIMITER $$
-- before inserting new id
DROP TRIGGER IF EXISTS before_insert_id$$
CREATE TRIGGER before_insert_id
BEFORE INSERT ON test FOR EACH ROW
BEGIN
-- condition to check
IF NEW.id < 0 THEN
-- hack to solve absence of SIGNAL/prepared statements in triggers
UPDATE `Error: invalid_id_test` SET x=1;
END IF;
END$$
DELIMITER ;
Using a stored procedure
Stored procedures allows you to use dynamic sql, which makes possible the encapsulation of the error generation functionality in one procedure. The counterpoint is that we should control the applications insert/update methods, so they use only our stored procedure (not granting direct privileges to INSERT/UPDATE).
DELIMITER $$
-- my_signal procedure
CREATE PROCEDURE `my_signal`(in_errortext VARCHAR(255))
BEGIN
SET #sql=CONCAT('UPDATE `', in_errortext, '` SET x=1');
PREPARE my_signal_stmt FROM #sql;
EXECUTE my_signal_stmt;
DEALLOCATE PREPARE my_signal_stmt;
END$$
CREATE PROCEDURE insert_test(p_id INT)
BEGIN
IF NEW.id < 0 THEN
CALL my_signal('Error: invalid_id_test; Id must be a positive integer');
ELSE
INSERT INTO test (id) VALUES (p_id);
END IF;
END$$
DELIMITER ;
The following procedure is (on mysql5) a way to throw custom errors , and log them at the same time:
create table mysql_error_generator(error_field varchar(64) unique) engine INNODB;
DELIMITER $$
CREATE PROCEDURE throwCustomError(IN errorText VARCHAR(44))
BEGIN
DECLARE errorWithDate varchar(64);
select concat("[",DATE_FORMAT(now(),"%Y%m%d %T"),"] ", errorText) into errorWithDate;
INSERT IGNORE INTO mysql_error_generator(error_field) VALUES (errorWithDate);
INSERT INTO mysql_error_generator(error_field) VALUES (errorWithDate);
END;
$$
DELIMITER ;
call throwCustomError("Custom error message with log support.");
CREATE TRIGGER sample_trigger_msg
BEFORE INSERT
FOR EACH ROW
BEGIN
IF(NEW.important_value) < (1*2) THEN
DECLARE dummy INT;
SELECT
Enter your Message Here!!!
INTO dummy
FROM mytable
WHERE mytable.id=new.id
END IF;
END;
Another (hack) method (if you are not on 5.5+ for some reason) that you can use:
If you have a required field, then within a trigger set the required field to an invalid value such as NULL. This will work for both INSERT and UPDATE. Do note that if NULL is a valid value for the required field (for some crazy reason) then this approach will not work.
BEGIN
-- Force one of the following to be assigned otherwise set required field to null which will throw an error
IF (NEW.`nullable_field_1` IS NULL AND NEW.`nullable_field_2` IS NULL) THEN
SET NEW.`required_id_field`=NULL;
END IF;
END
If you are on 5.5+ then you can use the signal state as described in other answers:
BEGIN
-- Force one of the following to be assigned otherwise use signal sqlstate to throw a unique error
IF (NEW.`nullable_field_1` IS NULL AND NEW.`nullable_field_2` IS NULL) THEN
SIGNAL SQLSTATE '45000' set message_text='A unique identifier for nullable_field_1 OR nullable_field_2 is required!';
END IF;
END
DELIMITER ##
DROP TRIGGER IF EXISTS trigger_name ##
CREATE TRIGGER trigger_name
BEFORE UPDATE ON table_name
FOR EACH ROW
BEGIN
--the condition of error is:
--if NEW update value of the attribute age = 1 and OLD value was 0
--key word OLD and NEW let you distinguish between the old and new value of an attribute
IF (NEW.state = 1 AND OLD.state = 0) THEN
signal sqlstate '-20000' set message_text = 'hey it's an error!';
END IF;
END ##
DELIMITER ;
Since MySQL ignores check constraints, how does one go about using a trigger to stop an insert or update from happening?
For example:
Table foo has an attribute called agency, and the agency attribute can only be 1, 2, 3, 4, or 5.
delimiter $$
create trigger agency_check
before insert on foo
for each row
begin
if (new.agency < 1 or new.agency > 5) then
#Do nothing?
end if;
end
$$
delimiter ;
Or is there a better way to go about doing check constraints in MySQL?
Try the SIGNAL syntax - https://dev.mysql.com/doc/refman/5.5/en/signal.html
create trigger agency_check
before insert on foo
for each row
begin
if (new.agency < 1 or new.agency >5) then
SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'your error message';
end if
end
EDIT
Updated based on popular comment below by Bill Karwin.
If your version of MySQL is older than 5.5, try setting a non-null field of the table to NULL. It is a hack, but it does prevent the update or insert from completing.
The SIGNAL command which Naveen suggests looks great, and I'm looking forward to using it after we upgrade.
Hi I need to write a trigger to check if the value is existing in a column, if yes then do not insert it and through and error.
There is a column which can have only two values(same as bool) DEFAULT or NONDEFAULT.
This column can have multiple NONDEFAULT value but only one DEFAULT value in column.
If the DEFAULT exists in table, we need to through an error and shall not insert the new row.
Kindly help
create trigger status_value before insert on TABLE for each row
begin
if new.status=DEFAULT AND select count(status) from TABLE where status=DEFAULT)
then
signal sqlstate = '4500'
set message_text = 'can not update, default value already present'
end if;
end;
Try it like this:
delimiter $$
create trigger status_value before insert on TABLE for each row
begin
if (new.status='DEFAULT' AND EXISTS (select 1 from TABLE where status='DEFAULT'))
then
signal sqlstate = '4500'
set message_text = 'can not update, default value already present';
end if;
end $$
delimiter ;
I'm assuming, that you mean the value of the column is a string "default", not the default value you defined when creating the table.
If I have a trigger before the update on a table, how can I throw an error that prevents the update on that table?
As of MySQL 5.5, you can use the SIGNAL syntax to throw an exception:
signal sqlstate '45000' set message_text = 'My Error Message';
State 45000 is a generic state representing "unhandled user-defined exception".
Here is a more complete example of the approach:
delimiter //
use test//
create table trigger_test
(
id int not null
)//
drop trigger if exists trg_trigger_test_ins //
create trigger trg_trigger_test_ins before insert on trigger_test
for each row
begin
declare msg varchar(128);
if new.id < 0 then
set msg = concat('MyTriggerError: Trying to insert a negative value in trigger_test: ', cast(new.id as char));
signal sqlstate '45000' set message_text = msg;
end if;
end
//
delimiter ;
-- run the following as seperate statements:
insert into trigger_test values (1), (-1), (2); -- everything fails as one row is bad
select * from trigger_test;
insert into trigger_test values (1); -- succeeds as expected
insert into trigger_test values (-1); -- fails as expected
select * from trigger_test;
Here is one hack that may work. It isn't clean, but it looks like it might work:
Essentially, you just try to update a column that doesn't exist.
Unfortunately, the answer provided by #RuiDC does not work in MySQL versions prior to 5.5 because there is no implementation of SIGNAL for stored procedures.
The solution I've found is to simulate a signal throwing a table_name doesn't exist error, pushing a customized error message into the table_name.
The hack could be implemented using triggers or using a stored procedure. I describe both options below following the example used by #RuiDC.
Using triggers
DELIMITER $$
-- before inserting new id
DROP TRIGGER IF EXISTS before_insert_id$$
CREATE TRIGGER before_insert_id
BEFORE INSERT ON test FOR EACH ROW
BEGIN
-- condition to check
IF NEW.id < 0 THEN
-- hack to solve absence of SIGNAL/prepared statements in triggers
UPDATE `Error: invalid_id_test` SET x=1;
END IF;
END$$
DELIMITER ;
Using a stored procedure
Stored procedures allows you to use dynamic sql, which makes possible the encapsulation of the error generation functionality in one procedure. The counterpoint is that we should control the applications insert/update methods, so they use only our stored procedure (not granting direct privileges to INSERT/UPDATE).
DELIMITER $$
-- my_signal procedure
CREATE PROCEDURE `my_signal`(in_errortext VARCHAR(255))
BEGIN
SET #sql=CONCAT('UPDATE `', in_errortext, '` SET x=1');
PREPARE my_signal_stmt FROM #sql;
EXECUTE my_signal_stmt;
DEALLOCATE PREPARE my_signal_stmt;
END$$
CREATE PROCEDURE insert_test(p_id INT)
BEGIN
IF NEW.id < 0 THEN
CALL my_signal('Error: invalid_id_test; Id must be a positive integer');
ELSE
INSERT INTO test (id) VALUES (p_id);
END IF;
END$$
DELIMITER ;
The following procedure is (on mysql5) a way to throw custom errors , and log them at the same time:
create table mysql_error_generator(error_field varchar(64) unique) engine INNODB;
DELIMITER $$
CREATE PROCEDURE throwCustomError(IN errorText VARCHAR(44))
BEGIN
DECLARE errorWithDate varchar(64);
select concat("[",DATE_FORMAT(now(),"%Y%m%d %T"),"] ", errorText) into errorWithDate;
INSERT IGNORE INTO mysql_error_generator(error_field) VALUES (errorWithDate);
INSERT INTO mysql_error_generator(error_field) VALUES (errorWithDate);
END;
$$
DELIMITER ;
call throwCustomError("Custom error message with log support.");
CREATE TRIGGER sample_trigger_msg
BEFORE INSERT
FOR EACH ROW
BEGIN
IF(NEW.important_value) < (1*2) THEN
DECLARE dummy INT;
SELECT
Enter your Message Here!!!
INTO dummy
FROM mytable
WHERE mytable.id=new.id
END IF;
END;
Another (hack) method (if you are not on 5.5+ for some reason) that you can use:
If you have a required field, then within a trigger set the required field to an invalid value such as NULL. This will work for both INSERT and UPDATE. Do note that if NULL is a valid value for the required field (for some crazy reason) then this approach will not work.
BEGIN
-- Force one of the following to be assigned otherwise set required field to null which will throw an error
IF (NEW.`nullable_field_1` IS NULL AND NEW.`nullable_field_2` IS NULL) THEN
SET NEW.`required_id_field`=NULL;
END IF;
END
If you are on 5.5+ then you can use the signal state as described in other answers:
BEGIN
-- Force one of the following to be assigned otherwise use signal sqlstate to throw a unique error
IF (NEW.`nullable_field_1` IS NULL AND NEW.`nullable_field_2` IS NULL) THEN
SIGNAL SQLSTATE '45000' set message_text='A unique identifier for nullable_field_1 OR nullable_field_2 is required!';
END IF;
END
DELIMITER ##
DROP TRIGGER IF EXISTS trigger_name ##
CREATE TRIGGER trigger_name
BEFORE UPDATE ON table_name
FOR EACH ROW
BEGIN
--the condition of error is:
--if NEW update value of the attribute age = 1 and OLD value was 0
--key word OLD and NEW let you distinguish between the old and new value of an attribute
IF (NEW.state = 1 AND OLD.state = 0) THEN
signal sqlstate '-20000' set message_text = 'hey it's an error!';
END IF;
END ##
DELIMITER ;