I need to edit a datatype (IS_NULLABLE) from my column tag.
Nothing works, i have tried like that:
ALTER TABLE veille
ALTER COLUMN tag
SET IS_NULLABLE false
or like that :
ALTER TABLE veille ALTER COLUMN tag Modify datatype false
but doesn't work too, i have this error :
Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'IS_NULLABLE false' at line 3.
Edit : Resolved, the problem was my column has null values, i have changed these null values and all works fine.
use
ALTER TABLE veille ALTER COLUMN tag datatype
columns are nullable by default, As long as the column is not declared UNIQUE or NOT NULL, there shouldn't be any problems.
refer to this question: How do I modify a MySQL column to allow NULL?
No need for datatype false
Just use the query like below
alter table table_name modify column tag <datatype> not null;
try ALTER TABLE veille_ndd_hist MODIFY tag bit(1) NOT NULL DEFAULT b'0;
you may also try ALTER TABLE veille_ndd_hist CHANGE COLUMN tag tag BIT NOT NULL
Note that when using MODIFY, you need to specify the full column definition, including DEFAULT value if was defined.
side note: of course make sure that the column does not have any null values
Related
I am writing a migration file in typeorm I wanted to add an extra column to my existing table.
I am writing the following query
await queryRunner.query('ALTER TABLE "me" ADD COLUMN "id" VARCHAR(255) DEFAULT NULL');
with the above query, I gt the following error:
RSE_ERROR: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '"me" ADD COLUMN "id" VARCHAR(255) DEFAULT NULL' at line 1,`
I just want that my column is nullable, also I want to set Collation to utf8mb4_bin.
How do I achieve that?
There is no need to double quote around table and column name.
ALTER TABLE me ADD COLUMN id VARCHAR(255) DEFAULT NULL;
Furthermore, the id column usually is auto increment int and primary key field.So if you want to name a string field id, it maybe ambiguous.
I have to add a varchar column to a table which defaults to the current timestamp. To do this I somehow need to convert the value from datetime to varchar.
I tried the following
ALTER TABLE `TableName`
CHANGE COLUMN `DocumentID` `DocumentID` VARCHAR(150) NULL DEFAULT CONVERT(NOW(), CHAR);
or
ALTER TABLE `TableName`
CHANGE COLUMN `DocumentID` `DocumentID` VARCHAR(150) NULL DEFAULT CONVERT(CURRENT_TIMESTAMP, CHAR);
I always get an error message, that my syntax is wrong. I am using MariaDB and HeidiSQL. Is there a way to do this?
EDIT: I am basically looking for a MySQL equivalent of the following SQL Server statement:
ALTER TABLE [dbo].[TableName] ADD CONSTRAINT [DF_TableName_DocumentID] DEFAULT (getdate()) FOR [DocumentID]
MariaDB document says
In MariaDB 10.2.1 you can use most functions in DEFAULT. Expressions
should have parentheses around them.
Hence you may check for the version of MariaDB and use the right syntax (parenthesis around expression):
(CONVERT(CURRENT_TIMESTAMP, CHAR))
Update
As an alternative, you may use Trigger to set the function value for the stable releases (< 10.2)
If you use CURRENT_TIMESTAMP as default value, you must use the datatype that the function retrieves, in this case is a timestamp as you can see in the docs.
I don't know the reasons that may lead you to save this as a varchar. I'm not sure but I think that MariaDB doesn't allow to call functions as default values so you can't convert CURRENT_TIMESTAMP as varchar. You have an alternative approach, make an after insert trigger updating the field (you can call CONVERT(CURRENT_TIMESTAMP, VARCHAR) inside a trigger).
Either way, I recomend to stay with timestamp.
I see the field is called "DocumentID", perhaps you want to save a hash value as identifier? You can archieve this with virtual columns. An example.
I already have a table, simplified example:
CREATE TABLE t (c INT NOT NULL);
And I need to change column default value to NULL, so I tried:
ALTER TABLE t ALTER COLUMN c SET DEFAULT NULL;
but I got the error "Error Code: 1067. Invalid default value for 'c'".
It looks really strange, because query conforms with official docs.
I even tried to:
ALTER TABLE t ALTER COLUMN c DROP DEFAULT;
and after it to make a 'SET DEFAULT NULL' query, but the same error occurred.
It's interesting, that query like:
ALTER TABLE t ALTER COLUMN c SET DEFAULT 1;
executed without errors.
I know, that it is possible to change column default value to NULL in my case using:
ALTER TABLE t MODIFY COLUMN c INT NULL;
but this query is really slow on big tables (it is much slower, than queries like 'SET DEFAULT 1')
So, how to just change default value to NULL?
I mean, without any overhead caused by 'MODIFY COLUMN' command.
Details: MySQL x64 version 5.7.10, Win8. Tested using MySQL Workbench.
By creating column as NOT NULL you have created a CONSTRAINT - declaring that values entered into that column may never be NULL.
A default value of NULL (set to null is value not present during INSERT) would create invalid data.
As sadly nullability constraint is part of the datatype in mysql the only way to make the column nullable will be
ALTER TABLE t MODIFY COLUMN c INT NULL;
When running
ALTER TABLE my_table modify column my_column int(10) NOT NULL DEFAULT 0;
I've got the error message:
Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'int(10) NOT NULL DEFAULT 0' at line 1.
How can this issue being fixed?
ALTER TABLE ... MODIFY COLUMN ... does not allow renaming the column; this is why the name of the column must be provided only once (the current name).
In order to rename the column (besides other changes you may want to operate on it, like changing its type) you have to use ALTER TABLE ... CHANGE COLUMN ... and provide the current and the new name of the column.
See the documentation page of the ALTER TABLE statement for more explanation and examples.
Try this code
ALTER TABLE my_table CHANGE mycolumn my_column INT( 10 ) NOT NULL DEFAULT '1';
I'm using PHPMyAdmin and I try to add the NOT NULL constraint to a column of my table.
PHPMyAdmin accepts my following query :
ALTER TABLE `wall` MODIFY `token_message` varchar(40) NOT NULL;
But I can still insert empty strings (=NULL), I don't understand why.
PS : If you're going to give me some other queries to add this constraint, note I've have tried these 3 which don't work in my PHPMyAdmin (kind of error : #1064 - You have an error in your SQL syntax; check the manual) :
ALTER TABLE `wall` ALTER COLUMN `token_message` SET NOT NULL;
ALTER TABLE `wall` ALTER COLUMN `token_message` varchar(40) NOT NULL;
ALTER TABLE `wall` MODIFY `token_message` CONSTRAINTS token_message_not_null NOT NULL;
You wrote, "I can still insert empty strings (=NULL)," which sounds like a misunderstanding. In SQL, an empty string does not evaluate to NULL, or vice versa. Try inserting an empty string and doing SELECT from wall where token_message is NULL. You should get zero rows back. Then try doing an insert where you specify NULL (unquoted) as the value for your column, and you should get the expected error message.
If those tests work as expected, then everything is fine, and your problem is actually that you want to prevent blank strings from being inserted. Check out this question for suggestions, or just check for blank strings during validation, before the query.
MySQL's column alter syntax requires you to completely re-specify the column. You can't just change one attribute of a column, you have to re-define it completely:
ALTER TABLE wall MODIFY token_message varchar(40) NOT NULL default ''
The only 'SET' version allowed is to change the default value.
ref: http://dev.mysql.com/doc/refman/5.1/en/alter-table.html
I think this is a matter of scrubbing your inputs. As octern mentioned, an empty string ('') is not a NULL value in sql. The best way to handle this is to only allow updates through a store procedure which strips out empty strings, even space characters:
CREATE PROC InsertIntoMyDb (#MyVarChar VARCHAR(2000)) AS
SET #MyVarChar = NULLIF(RTRIM(LTRIM(#MyVarChar)), '')
INSERT INTO [TBL] (MyVarChar)
VALUES #MyVarChar
This will truncate any number of spaces to an empty string, turn an empty string into a NULL, and then it will not allow the NULL value to be inserted based on the constraint you already have in place.
Try to use this query
Alter table table_name
change column_name column_name datatype(length) definition
ie,
Alter table wall
change tocken_message tocken_message varchar(40) NOT NULL DEFAULT