I'm trying to create some tables in HeidiSQL, the main key allows me to create it without any problem but when trying to create a foreign key I get error (1064) I would like to know if they could help.
Table 1. Where the main key is located
Table 2. Where the foreign key should go
Log in with Root
Create the tables
fill the tables with the given information
Create the main key in id_clientes
Create the foreign key in the table t_clientes put in the cell with the same name bearing the main key (id_clientes)
Those are at least the steps I have been given for this task but I will appear error 1064, even if I try to switch to another cell does not allow me the foreign key.
try this, I believe it will work
ALTER TABLE t_clientes
ADD CONSTRAINT id_clientes_fkey FOREIGN KEY (id_clientes)
REFERENCES t_ventas(id_clientes) MATCH SIMPLE
ON UPDATE CASCADE
ON DELETE RESTRICT
Related
I have added a table to a database called settings. This table has a column called id (integer) which is the pirmary key. I have also added a column called settingsID to a table called sessions. What I want to do is add a foreign key to settingsID which references the primary key.
I don't want to create a new table as it is already created. All I want to do is to references the id from the settings table in settingsID which is in sessions table.
ALTER TABLE Sessions ADD FOREIGN KEY (_SettingsID) REFERENCES settings (id)
Here is my error:
near "FOREIGN": syntax error
Can someone tell me the right way to approach this?
Short answer: you can't.
This is documented as part of the SQL Features That SQLite Does Not Implement:
Only the RENAME TABLE, ADD COLUMN, and RENAME COLUMN variants of the ALTER TABLE command are supported. Other kinds of ALTER TABLE operations such as DROP COLUMN, ALTER COLUMN, ADD CONSTRAINT, and so forth are omitted.
Bold emphasis is mine.
So basically you would need to create the constraint at the time when the table is created. For your use case, one solution would be to:
create a new table (with the foreign key constraint)
copy the data from the old table
drop the old table (or better yet, rename it, so you have a backup)
rename the new table
I have the problem similar to this one SQL Server foreign key conflict in a multi values statement? However, in sql server 2008.
While I am reading data from csv file, there is some id already not exist in parent and thus return this error:
INSERT statement conflicted with the FOREIGN KEY constraint
May I know if there is a way similar to MySQL insert ignore. Such that I can simply skip the problematic data.
I accept that if there is no method other than creating a stored procedure with a new temp table (insert into a table without foreign key first, and then re-insert with where foreign_id exists in (select id from parent)).
As I really cannot find any in documentation, asking for ensuring I didn't miss anything.
One general solution which comes to mind would be to temporarily turn off the foreign key constraints, and do the insert. Then, afterwards, you may run a cleanup script/query to remove or rectify child records which are pointing to parents which do not exist. Once your data is in good shape, then turn on the foreign key constraints again.
Read How can foreign key constraints be temporarily disabled using T-SQL? to learn how to disable/enable a foreign key constraint for a single table:
ALTER TABLE MyTable NOCHECK CONSTRAINT MyConstraint -- disable
ALTER TABLE MyTable WITH CHECK CHECK CONSTRAINT MyConstraint -- enable
When I have SQL Server Management Studio generate a table creation script for me, the foreign key constraints are a bit different than how I would write them.
Here is one:
ALTER TABLE [dbo].[GeoBytesCountries]
WITH CHECK
ADD CONSTRAINT [FK_GeoBytesCountries_MapReferenceId]
FOREIGN KEY ([MapReferenceId])
REFERENCES [dbo].[GeoBytesMapReferences] ([MapReferenceId])
GO
ALTER TABLE [dbo].[GeoBytesCountries]
CHECK CONSTRAINT [FK_GeoBytesCountries_MapReferenceId]
GO
I would write this foreign key constraint without "WITH CHECK" and the 2nd "CHECK CONSTRAINT" statement and expect to get the same functionality.
Can someone explain to me the value of the using "WITH CHECK" and a separate "CHECK CONSTRAINT" statement when you are writing a foreign key constraint for a table?
Or is the code below completely / functionally equivalent to the code above?
ALTER TABLE [dbo].[GeoBytesCountries]
ADD CONSTRAINT [FK_GeoBytesCountries_MapReferenceId]
FOREIGN KEY ([MapReferenceId])
REFERENCES [dbo].[GeoBytesMapReferences] ([MapReferenceId])
GO
The way I see it, the two step approach allows you to at least keep more "bad" data from getting in assuming the with check part fails. That is, your constraint will exist and apply to DML from that point forward, but you may have to do some cleanup on your existing data to make it a trusted constraint.
Using:
ALTER TABLE dbo.Table1Name
ADD FOREIGN KEY (colname)
REFERENCES dbo.Table2Name (colname)
I get a foreign key with a name like:
FK___colname__673F4B05
I want it to be named:
FK_Tabl1Name_Table2Name,
...so that it will be easy to read when browsing the DB structure in SSMS. I know I can go back into the GUI and do this, but I want to be able to script it.
So What's the SQL sytnax for adding a name to the FK? Nothing I've found online seems to bother with this.
Here's how you can assign your chosen name to the foreign key constraint:
ALTER TABLE dbo.Table1Name
ADD CONSTRAINT FK_Tabl1Name_Table2Name
FOREIGN KEY (colname) REFERENCES dbo.Table2Name (colname)
How do i delete a foreign key constraint programmatically in Microsoft Access, preferable using SQL. For starters i don't know how to find the name of the foreign key.
I connect to Access from a Java application using the JDBC-ODBC bridge. I want to execute the SQL from my Java application.
I can see the relationship in Access, in the RelationShip view, but there seems to be no way of finding out the name. If i could find out the name i expect i could drop it with an ALTER TABLE statement.
Determine the relationship using
SELECT szRelationship FROM
Msysrelationships WHERE szObject =
'childtablename' and
szReferencedObject = 'parenttablename'
THEN
Use the ALTER TABLE command. Something along the line of this
ALTER TABLE Table2 DROP CONSTRAINT Relation1
I've tried accessing the foreign key name via JDBC's DataBaseMetadata object, but the JDBC-ODBC bridge does not implement the required functions. So i've resorted to droping and recreating the entire table with the foreign key.