I have encountered a problem in that I already have a composite primary key in a MYSQL table. But now I have added another column to that table and due to some requirement changes, I have to modify that composite primary key in such a way that I need to add that previously mentioned column to that composite primary key list. Can anyone tell me how to alter that table without dropping existing composite primary key. I am doing this in a Rails project
You can't alter the primary key. You have to drop and re-add it:
ALTER TABLE MyTable
DROP PRIMARY KEY,
ADD PRIMARY KEY (old_col1, old_col2, new_col);
but if a key no exist?
example:
ALTER TABLE xxxx ADD id INT NOT NULL AUTO_INCREMENT, ADD PRIMARY KEY(id,id2,id3);
Related
I've first table name "mustahik_perorangan" and the second name "data_mustahik"
mustahik perorangan have 4 primary key and foreign key in another table
like this condition
PRIMARY KEY (`mustahik_nik`,`ins_provinces_code`,`ins_cities_code`,`ins_institution_types_code`,`ins_institution_serial_no`),
KEY `fk_reference_6` (`ins_provinces_code`,`ins_cities_code`,`ins_institution_types_code`,`ins_institution_serial_no`),
CONSTRAINT `FK_ins_musper` FOREIGN KEY (`ins_provinces_code`, `ins_cities_code`, `ins_institution_types_code`, `ins_institution_serial_no`) REFERENCES `baznasgo_s_organization`.`institutions` (`provinces_code`, `cities_code`, `institution_types_code`, `institution_serial_no`) ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=latin1
and i want to add primary to table mustahik_perorangan, so mustahik perorangan have 5 primary key ?
but i can't do it because it condition..
ALTER TABLE mustahik_perorangan ADD idc INT UNSIGNED NOT NULL AUTO_INCREMENT,ADD PRIMARY KEY (`idc`);
May you know to do it ?
A table can have at most one primary key constraint.
The primary key constraint can contain multiple columns. We refer to that as a composite key.
It is possible to add a new column.
It's also possible to add a UNIQUE constraint on the column and specify AUTO_INCREMENT attribute on the column.
As an example:
ALTER TABLE mustahik_perorangan
ADD idc INT UNSIGNED NOT NULL AUTO_INCREMENT
, ADD UNIQUE KEY (`idc`)
It's also possible to a sixth column to the existing composite primary key. But I don't think this is what you really want.
As a demonstration of how to add a column to an existing composite primary key, I'll provide an example.
Note that the primary key must be dropped and re-added. And a UNIQUE key must be added for the AUTO_INCREMENT column.
Assuming there are no foreign keys referencing the primary key of this table.
ALTER TABLE mustahik_perorangan
DROP PRIMARY KEY
, ADD idc INT UNSIGNED NOT NULL AUTO_INCREMENT
, ADD UNIQUE KEY (`idc`)
, ADD PRIMARY KEY
(`mustahik_nik`
,`ins_provinces_code`
,`ins_cities_code`
,`ins_institution_types_code`
,`ins_institution_serial_no`
,`idc`
)
If there are foreign keys referencing the table, the change is a little more involved. (Did you want an additional column added to the foreign keys in the referencing tables?)
It's not entirely clear what you are attempting to achieve.
Yes, you can add the primary key, but in your case, you need to drop pk and then add new pk, otherwise the engine interpretes as you are trying to add multiple pks, the multiple pks are different from composite pk, you can add composite pk, but you can't add multiple pks
alter table xx drop primary key, add primary key(k1, k2, k3);
I have a Mysql table having the following structure:
As you can see there is a composite primary key constraint between the fields: word_id and preposition_id.
I want to remove the Primary Key constraint from word_id without touching the preposition_id field, and without losing data from the linked tables (Foreign Key tables). How can I do it?
Regards.
There is no syntax available to modify a constraint and drop only "a half" of the primary key.
You must drop the whole primary key, and then recreate it from scrach.
Just:
ALTER TABLE tablename DROP PRIMARY KEY;
and then:
ALTER TABLE tablename ADD PRIMARY KEY ( preposition_id );
You need first to drop all foreign keys thar reference the primary key in this table.
Data in tables will be preserved.
I know how to add a primary key when creating the table, but not how to add it to an existing table. Do I need to create a column and then change the type to a primary key, or use something like this:
ALTER TABLE table-name MODIFY column-name PRIMARY KEY;
You can add primary key the table by;
ALTER TABLE table_name
ADD PRIMARY KEY(primary_key_column);
If you want composite primary key(primary key of more than on column) then,
ALTER TABLE table_name
ADD PRIMARY KEY(column_1, column_2);
If you have already a primary key and you want to drop existing and add another
then,
ALTER TABLE table_name
DROP PRIMARY KEY, ADD PRIMARY KEY(primary_key_column);
I want to change primary key of table, initially it was id, now i want to change it to userid
smsusers(id,fname,lname,userid)
Here id is varchar type
adn userid is int type
for this i am trying following query
ALTER TABLE smsusers DROP PRIMARY KEY
which is showing this error
#1025 - Error on rename of '.\xrcwrn_sms\#sql-ae0_6f' to
'.\xrcwrn_sms\smsusers' (errno: 150)
id of smsusers is associated with many tables as foreign key.
How to change the primary key.
Here is an example:
ALTER TABLE `database`.`table`
DROP PRIMARY KEY,
ADD PRIMARY KEY (`userid`);
The message is telling you that you can't drop the primary key yet because it is referenced by one or more foreign keys. You need to identify and drop the foreign keys first, then drop the primary key.
ERROR NO:150 means Foreign key definition problem. I think that some other table has a foreign key constraint depending on this PK, so you need to drop that first and rebuild it later.
I tried this link. This is working properly.
My steps are
CREATE INDEX id_pk_unique ON smsusers (id)
ALTER TABLE parent DROP PRIMARY KEY;
ALTER TABLE parent ADD PRIMARY KEY (userid);
I'm creating a table that has a basisId field as the primary key. There's also another field parentBasis which would be a reference to another tuple with that.basisId equal to this.parentBasis. What I want to do to is express this constraint while creating the table.
Something like: ADD CONSTRAINT CHECK EXISTS this.parentBasis AS somewhere.basisId (Obviously not real MySQL).
A quick browse through the MySQL dev pages didn't do much good. Any help would be appreciated.
Thanks.
If you're using InnoDB then you can create a foreign key from the table to itself. For example:
create table t (
id int not null primary key,
parent int null
);
alter table t add constraint foreign key (parent) references t(id);
then t.parent would either have to be NULL or a t.id value.