I'm trying to alter current id field in organization table to UUID_SHORT but failed?
ALTER TABLE `organization` CHANGE `id` `id` BIGINT(16) UNSIGNED
NOT NULL DEFAULT uuid_short();
I don't see any error message?!
I don't think you can set the default value for id like this
Rather you can create a trigger to do this:
CREATE TRIGGER before_insert_organization
BEFORE INSERT ON organization
FOR EACH ROW
SET new.id = uuid_short();
Related
I've a table item that has some columns that are nullable.
To one of them type, I'd like to automatically insert a default value (instead of a NULL) whenever a new record in inserted in the table and do not specify a value for that column.
Can it be done without affecting the existing data?
The type column is a varchar.
I can update the current nulls.
You can try to ALTER column set a default value.
ALTER TABLE `T` MODIFY `type` varchar(50) DEFAULT 'default';
then insert by DEFAULT keyword:
INSERT INTO T (type) VALUES (DEFAULT);
Results:
This query will work for you.
For update table.
ALTER TABLE `column_name` CHANGE `tab` `my_id` INT(11) NOT NULL DEFAULT '0';
For insert table
CREATE TABLE `db_name`.`Tbale_name` ( `demo` INT NOT NULL DEFAULT '0');
How can i make a table field with default value "none" and null value "no"?
When i create a table with following code it always add default value NULL and null to yes
ALTER TABLE `table_name` ADD `test` INT(11) AFTER `test1`
ALTER TABLE `table_name` ADD `test` INT NOT NULL AFTER `test1`;
ALTER TABLE myTable
ALTER column SET DEFAULT 'none'.
For replacing NULL with NO you don't have to alter the table just do it in your query :
SELECT COALESCE(columnWhichisNull,'no'))
FROM myTable ;
COALESCE checks if a value from a column is null and replaces it with your desired character
I want to create a column with default value as null and when any operation is performed it should change to 0. How do i do this in mysql database?
Here example how to add colum in existing table with default value
ALTER TABLE `test1` ADD `no` INT NULL DEFAULT NULL ;
When you call function then you have to write following query
UPDATE test1 SET `no` = '0' WHERE `test1`.`id` =your_id;
CREATE TABLE test
(
id INT NOT NULL AUTO_INCREMENT,
PRIMARY KEY(id),
test_id INT,
cost FLOAT(5,2) DEFAULT NULL,
);
each time when you do some operation on that you need to update it as #Sadikhasan
or write a trigger that will update it to zero automatically.
if the operation you want to perform is read then write trigger on ON SELECT
if the operation you want to perform is update then write trigger on ON UPDATE
like wise for others.
I create my borrowed table that keeps which users borrowed which books records of a library application.
I forgot to set not null When i create userID and bookID fields,
how i can add this feature ti this two fields?
I try this but failed:
Alter table borrowed set not null (userID,bookID);
In mysql you can add a costraint in an existing column with the command MODIFY:
ALTER TABLE borrowed MODIFY userID INT(11) NOT NULL;
ALTER TABLE borrowed MODIFY bookID INT(11) NOT NULL;
You can do so by using the CHANGE syntax separated by comma for multiple columns
ALTER TABLE `borrowed`
CHANGE `userID` `userID` INT(11) NOT NULL,
CHANGE `bookID` `bookID` INT(11) NOT NULL;
this is my tables
CREATE TABLE IF NOT EXISTS `carslibrary` (
`CarID` int(10) unsigned NOT NULL AUTO_INCREMENT,
`CarName` varchar(255) NOT NULL,
PRIMARY KEY (`CarID`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ;
CREATE TABLE IF NOT EXISTS `colorslibrary` (
`ColorID` int(11) unsigned NOT NULL AUTO_INCREMENT,
`ColorName` varchar(255) NOT NULL,
PRIMARY KEY (`ColorID`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=5 ;
CREATE TABLE IF NOT EXISTS `facerecord` (
`carslibrary_ID` int(10) unsigned NOT NULL,
`colorslibrary_ID` int(11) unsigned NOT NULL,
KEY `carslibrary_ID` (`carslibrary_ID`),
KEY `colorslibrary_ID` (`colorslibrary_ID`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
i noticed carslibrary_ID attribute inside facerecord table is not automatically updated when i add a car record inside carslibrary table, what should i do to be able to?
Firstly, you'll need to have a default value specified for the facerecord.colorslibrary_ID since you will not 'know' what it is when inserting into the carslibrary table. That said you could alter your DDL for the facerecord table to be:
CREATE TABLE `facerecord` (
`carslibrary_ID` int(10) unsigned NOT NULL,
`colorslibrary_ID` int(10) unsigned NOT NULL DEFAULT '0',
KEY `carslibrary_ID` (`carslibrary_ID`),
KEY `colorslibrary_ID` (`colorslibrary_ID`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
I've also changed the datatype of the colorslibrary_ID column to match that of the colorslibrary.ColorID column in case you ever feel like setting up a foreign key between facerecord.colorslibrary_ID and colorslibrary.ColorID ;). For the sake of completeness you should insert a row into the colorslibrary table with a ColorID = 0. Hence:
insert into `colorslibrary` (ColorName) values ('unknown color');
update `colorslibrary` set ColorID = 0 where ColorName = 'unknown color';
Then you can go ahead and define your trigger to insert into the facerecord table:
delimiter $$
CREATE TRIGGER carslibrary_trigger
AFTER insert ON carslibrary
FOR EACH ROW
BEGIN
insert into facerecord (carslibrary_ID) values (new.CarID);
END$$
delimiter;
All new rows inserted into the facerecord table will then be inserted with a colorslibrary_ID that relates to the 'unknown color' colorslibrary.ColorName.You can then manually update the facerecord.colorslibrary_ID as and when you know it.
Good luck!
PS If you need to remove any existing AFTER insert triggers from the carslibrary table you can do so by firstly finding the existing triggers:
select trigger_name
from information_schema.triggers
where event_object_table = 'carslibrary'
and action_timing = 'AFTER'
and event_manipulation= 'INSERT';
Then take the name of the trigger returned by the above statement (lets say the string 'carslibrary_trigger' is returned) and run:
drop trigger carslibrary_trigger;
Then re-run the CREATE TRIGGER script.
Once a trigger is set up it will automatically perform the action you have specified when the trigger action you have specified occurs. In this case we are telling the database "after an insert happens into the carslibrary table automatically insert a row into the facerecord table using the CarID of the new carslibrary row to populate the facerecord.carslibrary_ID column". As with most things the best way is to try it! Once you have created the trigger manually insert a new row into the 'carslibrarytable. Now look at the data in thefacerecord` table - you should see a new row that has been inserted by the trigger firing.
It sounds like you would benefit from learning about triggers. I recommend the docs on the MySQL site because this answer is way longer than I first intended it to be!
You will need to use triggers. See http://dev.mysql.com/doc/refman/5.0/en/triggers.html