ALTER TABLE `pages` MODIFY `views` INT(11) NOT NULL DEFAULT 0
Trying to alter a column in a table which is currently allows NULL and has no default.
I want it to be NOT NULL and have a default of 0.
The Error message I get is
Invalid use of NULL value
This is because the table already has a row or more with null value, you might need to update those to 0 before executing ALTER table, e.g.:
UPDATE test SET views = 0 WHERE views IS NULL;
ALTER TABLE test MODIFY COLUMN views int NOT NULL DEFAULT 0;
Here's the SQL Fiddle (commenting out update statement will result in the same error).
Related
I want to edit a column in a MySQL table. Right now, it is tinyint with value NULL. I want to change the value to '0'. I tried using this expression:
ALTER TABLE hosts MODIFY COLUMN hide TINYINT NOT NULL DEFAULT 1;
and this
ALTER TABLE hosts MODIFY COLUMN hide TINYINT DEFAULT 1 NOT NULL;
and more variations. But this didn't work for me..
I get this error
EXECUTE FAIL:
ALTER TABLE hosts MODIFY COLUMN hide TINYINT(1) DEFAULT 0 NOT NULL
Message :
Invalid use of NULL value
What's the problem and what is the correct statement?
You cannot alter the table to „not null“ as long as you have data in it with null value.
First set all you data to 0
Update hosts set hide = 0 where hide is null
I'm trying to modify a row, marketing_schedule, in my database to change the column to NULL to NO.
I've tried the command ALTER TABLE permissions MODIFY marketing_schedule tinyint(1) NOT NULL; as given in How to add not null constraint to existing column in MySQL5.1 but I get the error shown in the screenshot above. Any idea on why I'm getting this error and how I can go about fixing my problem?
Update rows which have NULL's in marketing_schedule to have a value and run the ALTER TABLE command again.
If your are providing the default not null then you have to provide default value
in query
These query run after the update , as answered by #slaakso
ALTER TABLE `table_name` Modify `column_name` TINYINT(4) DEFAULT 1 NOT
NULL;
OR
ALTER TABLE `table_name` CHANGE `column_name` `column_name` TINYINT(4)
DEFAULT 1 NOT NULL;
Here 1 is default value
Is it possible to set a default value for new records only in a mysql column?
I want all rows before today to be null if nothing has been entered, but any new rows added after today to be a specific string if nothing has be entered for that column.
Is this possible?
Search in all rows in the table and check if the specific column is empty, if yes set it to null.
UPDATE tablename SET column = CASE column WHEN '' THEN NULL ELSE column END
For future entries you can add to your table a Default Constraint like this:
ALTER TABLE tablename ALTER column SET DEFAULT 'specific string'
This is an old post but I do think this answer might help other folks.
ALTER TABLE object_table_name ADD `value` INT NULL;
ALTER TABLE object_table_name MODIFY COLUMN `value` INT DEFAULT 0;
Doing it this way will only impact newly inserted records, this code did not work for me
ALTER TABLE object_table_name ADD `value` INT DEFAULT 0
I'm using MySQL 5.6
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 was wanting a mysql trigger for a specific field. When a NULL value is inserted into this field I would like to replace it with a default value. I know this code is not correct, but it would give you an idea of what I want.
CREATE TABLE IF NOT EXISTS example(
id INT NOT NULL AUTO_INCREMENT,
parent_id INT NOT NULL
);
CREATE TRIGGER insert_parentId_trigger BEFORE INSERT ON example
FOR EACH ROW BEGIN
IF parent_id = NULL THEN
SET parent_id = 0;
END IF
END;
Declare that column with not null default 0 instead of using trigger later.
When mysql is already handling that condition why we need to use trigger here?
You can use alter command to update your definition of your column
ALTER TABLE example MODIFY parent_id INT(11) NOT NULL DEFAULT 0
I agree with the example of a Null be simplistically set to 0, then using a "Default" is fine, but what if you're after a value that's variable and cannot be a Default? For example:
IF `Creator` Is NULL THEN
SET `Creator` = current_user();
END IF
For this type of use case, or something that requires a lookup, you will not be able to use Default.
Besides that Shakti Singh is totally right with the default value, you have to compare NULL values with IS instead of =
It should be IF parent_id IS NULL