Using Auto-Increment value in MYSQL Before Insert Trigger?
The users table:
CREATE TABLE `users` ( `id` int(8) unsigned NOT NULL AUTO_INCREMENT, `email` varchar(45) DEFAULT NULL, `username` varchar(16) DEFAULT NULL, `salt` varchar(16) DEFAULT NULL, `password` varchar(128) DEFAULT NULL, `lastlogin` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00', `joined` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, `loggedin` tinyint(1) unsigned NOT NULL DEFAULT '0', `sessionkey` varchar(60) DEFAULT NULL, `verifycode` varchar(16) DEFAULT NULL, `verified` tinyint(1) unsigned NOT NULL DEFAULT '0', `banned` tinyint(1) unsigned NOT NULL DEFAULT '0', `locked` tinyint(1) unsigned NOT NULL DEFAULT '0', `ip_address` varchar(45) DEFAULT NULL, `failedattempts` tinyint(1) unsigned NOT NULL DEFAULT '0', `unlocktime` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00', PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=latin1;
The user_records table:
CREATE TABLE `user_records` ( `id` int(8) unsigned NOT NULL AUTO_INCREMENT, `userid` int(8) unsigned DEFAULT NULL, `action` varchar(100) DEFAULT NULL, `timestamp` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=latin1;
The before insert trigger on the users table:
USE `gknet`; DELIMITER $$ CREATE DEFINER=`root`@`localhost` TRIGGER `before_create_user` BEFORE INSERT ON `users` FOR EACH ROW BEGIN INSERT INTO user_records (action, userid, timestamp) VALUES ('CREATED', ID, NOW() ); END
Basically, my problem here is that on the trigger when I try to put in the id of the user that's automatically assigned by MySQL (PK, NN, Auto-Increment), it just puts in 0 for userid on the user_records table. How would I do it so it would select the id that the user is being assigned by SQL, and put it in as userid on the records entry (where the ID is right after 'CREATED')?
Also, if you see any other optimizations that could be made on the tables, feel free to let me know :D
OP's comment: How would I do it before, thou?
You can find current
auto_increment value that is to be assigned to a new record.
And use the same in the
before trigger as a parent user id for
You have to query
information_schema.tables table to find the value.
use `gknet`; delimiter $$ drop trigger if exists before_create_user; $$ create definer=`root`@`localhost` trigger `before_create_user` before insert on `users` for each row begin declare fk_parent_user_id int default 0; select auto_increment into fk_parent_user_id from information_schema.tables where table_name = 'users' and table_schema = database(); insert into user_records ( action, userid, timestamp ) values ( 'created', fk_parent_user_id, now() ); end; $$ delimiter ;
Observations: As per mysql documentation on last_insert_id(),
"if you insert multiple rows using a single INSERT statement,
LAST_INSERT_ID()returns the value generated for the first inserted row only."
hence, depending on
auto_increment field values in batch inserts seems not reliable.
MySQL BEFORE INSERT Trigger Explained by Practical Examples, Column b: Dependent on a (value needs to be computed using the Now i created BEFORE INSERT trigger, problem now is that i cannot� You can find current auto_increment value that is to be assigned to a new record. And use the same in the before trigger as a parent user id for user_records table. You have to query information_schema.tables table to find the
Change the trigger to
after insert instead of
before insert and use
NEW to get the last inserted id
USE `gknet`; DELIMITER $$ CREATE DEFINER=`root`@`localhost` TRIGGER `after_create_user` AFTER INSERT ON `users` FOR EACH ROW BEGIN INSERT INTO user_records (action, userid, timestamp) VALUES ('CREATED', NEW.ID, NOW() ); END; $$
Accessing auto-increment value in Trigger, The AUTO_INCREMENT attribute can be used to generate a unique identity for new When you insert any other value into an AUTO_INCREMENT column, the � Auto increment for InnoDB keeps incrementing from the last value, it will not start numbering again even if the string changes Like I said this is to model existing an existing legacy system (in DB2) but I've been using MySQL fine up till now But I do need this behavior.
PLEASE USE AFTER INSERT AND UPDATE
Do not make auto_increment any column you want to manipulate explicitly. That can confuse an engine and cause serious problems. If no column you have used for primary key are auto_increment you can do anything you want with them via triggers. Sure generated values will be rejected if they violate the mandatory uniqness of the primary key.
MySQL Tutorial :: 7.9 Using AUTO_INCREMENT, This MySQL tutorial explains how to create a BEFORE INSERT Trigger in You can learn more about how we use advertisements here. CREATE TRIGGER trigger_name BEFORE INSERT ON table_name FOR EACH ROW BEGIN -- variable NOT NULL AUTO_INCREMENT, last_name VARCHAR(30) NOT NULL,� Now i created BEFORE INSERT trigger, problem now is that i cannot access the autoincrement value as the a column returns 0! How do i access the autoincrement value in trigger? Workaround: I accessed the value from the information schema database. Steps followed: 1. Access the auto increment value 2. Set column b's value
maybe this solution can
BEGIN DECLARE id int; SELECT MAX(table_id) FROM table INTO id; IF id IS NULL THEN SET NEW.column=(CONCAT('KTG',1)); ELSE SET NEW.column=(CONCAT('KTG',id+1)); END IF; END
MySQL: BEFORE INSERT Trigger, In MySQL you can insert directly into AUTO_INCREMENT Column. So, take this example from MySQL manual: CREATE TABLE animals ( id MEDIUMINT NOT� Second, use BEFORE INSERT clause to specify the time to invoke the trigger. Third, specify the name of the table that the trigger is associated with after the ON keyword. Finally, specify the trigger body which contains one or more SQL statements that execute when the trigger is invoked.
ALTER TABLE AUTO_INCREMENT number in a Trigger, Quick Example: -- Define a table with an auto-increment column (id starts at 100) To generate a ID value, you can omit the auto-increment column in INSERT OR REPLACE TRIGGER airlines_seq_tr BEFORE INSERT ON airlines FOR� In a BEFORE trigger, the NEW value for an AUTO_INCREMENT column is 0, not the sequence number that is generated automatically when the new row actually is inserted. By using the BEGIN END construct, you can define a trigger that executes multiple statements.
MySQL - AUTO_INCREMENT, I would like to set a trigger where upon inserting a new record with permalink set to CREATE TRIGGER article_filename BEFORE INSERT ON I was doing above but then I don't get the value of the auto-incremented field. Let's look at an example of how to create an BEFORE INSERT trigger using the CREATE TRIGGER statement in MySQL. If you had a table created as follows: CREATE TABLE contacts ( contact_id INT(11) NOT NULL AUTO_INCREMENT, last_name VARCHAR(30) NOT NULL, first_name VARCHAR(25), birthday DATE, created_date DATE, created_by VARCHAR(30), CONSTRAINT
MySQL triggers, Prior to Oracle's version 12c, there was no way to generate auto incrementing columns that multiple users can access to automatically generate incremented values. primary key for a new table, first we must CREATE the table we'll be using: we want the trigger to fire BEFORE INSERT occurs for the books table, and to� 1.to Update the new row Use BEFORE INSERT ON trigger, this way you can update all the fields for the new row, which can be accessible via NEW operator i.e. set NEW.group_id = NEW.id 2.Get auto_increment value before insert: SELECT AUTO_INCREMENT FROM information_schema.TABLES WHERE TABLE_SCHEMA=DATABASE() AND TABLE_NAME='MyTable'