I want to assign a value as default for a column.
It says that there is a syntax error at line 2 :
SELECT `id` into #idND FROM `xxx` WHERE `name`='John';
ALTER TABLE `xxx2` CHANGE `statut_id` `statut_id` TINYINT(4) NULL DEFAULT #idND;
It works if I set DEFAULT 3 for example. What am I doing wrong please ?
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).
How to set varchar, text, int default to NULL in Mysql?
I have a table, some columns are optional for the user to fill.
I want to set the default to NULL if the user didn't fill any thing.
I try to do it in PHPMyAdmin, but I got error #1067 - Invalid default value
Make sure that the option Null for the column be checked.
I have to add a column whose default value is not null by default to the table after particular column using Alter table.
ALTER TABLE tblechecklistrevision ADD COLUMN IWorkFlowOrder INT(10) DEFAULT NOT NULL AFTER fState;
When I Execute the query I will get the below 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 'NOT NULL AFTER fState' at line 1
You should remove DEFAULT:
ALTER TABLE tblechecklistrevision
ADD COLUMN IWorkFlowOrder INT(10) NOT NULL AFTER fState;
DEFAULT is for setting initial value to new rows where a value for that column isn't specified, when you write ...INT(10) NOT NULL what you mean is actually that that column can never contain a NULL, not only at initialization time.
If you want the default value not to equal NULL (example 0) you can do:
ALTER TABLE tblechecklistrevision
ADD COLUMN IWorkFlowOrder INT(10) NOT NULL DEFAULT 0 AFTER fState
I hope this isn't a dumb question. You can set a default value for all variables or a function for when it is inserted. but if the field is not required to insert and you don't allow null values, what is the "blank" value that you see in phpMyAdmin? in a query is it returned as empty string, etc?
just trying to figure it out, I want to query for all records such that the value for a specific column in that record is not "empty" or blank or whatever.
thanks.
Referring to the manual,
For data entry for a NOT NULL column that has no explicit DEFAULT
clause, if an INSERT or REPLACE statement includes no value for the
column, or an UPDATE statement sets the column to NULL, MySQL handles
the column according to the SQL mode in effect at the time:
If strict SQL mode is not enabled, MySQL sets the column to the implicit default value for the column data type.
If strict mode is enabled, an error occurs for transactional tables and the statement is rolled back. For nontransactional tables, an
error occurs, but if this happens for the second or subsequent row of
a multiple-row statement, the preceding rows will have been inserted.
So your question now may be, what are the implicit default values for the various column data types? Here you go:
Implicit defaults are defined as follows:
For numeric types, the default is 0, with the exception that for integer or floating-point types declared with the AUTO_INCREMENT
attribute, the default is the next value in the sequence.
For date and time types other than TIMESTAMP, the default is the appropriate “zero” value for the type. For the first TIMESTAMP column
in a table, the default value is the current date and time. See Section 10.3, “Date and Time Types”.
For string types other than ENUM, the default value is the empty string. For ENUM, the default is the first enumeration value.
There IS no default value unless you specify one (i.e. unless you define a "default constraint" for the column in question).
Here's an example for adding a default on an existing column:
ALTER TABLE dbo.customer ALTER COLUMN contactname SET DEFAULT 'Unknown'
Here's an example creating the table with a default:
CREATE TABLE Books (
ID SMALLINT NOT NULL,
Name VARCHAR(40) NOT NULL,
PubID SMALLINT NOT NULL DEFAULT 0
)
It's good practice to declare ALL columns "not null", and provide default constraints as appropriate.
In the "books" example above, if you "insert" without specifying PubID, the PubID will be zero.
In the same example, if you "insert" without specifying ID or Name ... you'll get an error.
If you want MySQL to auto-assign an ID, use this syntax instead:
CREATE TABLE Books (
ID SMALLINT NOT NULL AUTO_INCREMENT,
Name VARCHAR(40) NOT NULL,
PubID SMALLINT NOT NULL DEFAULT 0
)
If you want to disallow null :-
alter table YOUR_TABLE modify column COLUMN varchar(255) not null default '';
The above query will disallow null and assign an empty string when the value is not supplied.
In phpmysqladmin, blank = empty.
Via PHP mysqli function or mysql function, null value is returned as null still.
Once you have apply the query, you can easily filter that by using
select ... from YOUR_TABLE
where COLUMN != ""; <-- no need to check is null
<-- because the first query already enforce not null
However, is best for you do this before perform the alter :-
update YOUR_TABLE set COLUMN = ""
where COLUMN is null;