foreign-keys

I have searched for an answer but am not finding it. I have 2 tables. Both have an auto-generated PK. The PK from table 2 is an FK in table 1. Since they are both auto-generated I assumed the FK in table 1 would populate with the value that is auto-generated from table 2 but it is not working. The FK in table 1 ends up null. Here is my SQL code for creating table 1: CREATE TABLE Employee_tbl ( EmployeeID int PRIMARY KEY IDENTITY, LastName varchar(20) not null, FirstName varchar(20) not null, Age varchar(3) not null, JobID int FOREIGN KEY REFERENCES JobTitle_tbl(JobID), ) and here is table 2:

I would like to add a constraint that will check values from related table. I have 3 tables: CREATE TABLE somethink_usr_rel ( user_id BIGINT NOT NULL, stomethink_id BIGINT NOT NULL ); CREATE TABLE usr ( id BIGINT NOT NULL, role_id BIGINT NOT NULL ); CREATE TABLE role ( id BIGINT NOT NULL, type BIGINT NOT NULL ); (If you want me to put constraint with FK let me know.) I want to add a constraint to somethink_usr_rel that checks type in role ("two tables away"), e.g.: ALTER TABLE somethink_usr_rel ADD CONSTRAINT CH_sm_usr_type_check CHECK (usr.role.type = 'SOME_ENUM'); I tried to do this with

We have a database in which one table contains records that can be child to several other tables. It has a "soft" foreign key consisting of the owner's Id and a table name. This (anti) pattern is know as "polymorphic associations". We know it's not the best database design ever and we will change it in due time, but not in the near future. Let me show a simplified example: Both Event , Person , and Product have records in Comment. As you see, there are no hard FK constraints. In Entity Framework it is possible to support this model by sublassing Comment into EventComment etc. and let Event

We're trying to rename a column in MySQL (5.1.31, InnoDB) that is a foreign key to another table. At first, we tried to use Django-South, but came up against a known issue: http://south.aeracode.org/ticket/243 OperationalError: (1025, "Error on rename of './xxx/#sql-bf_4d' to './xxx/cave_event' (errno: 150)") AND Error on rename of './xxx/#sql-bf_4b' to './xxx/cave_event' (errno: 150) This error 150 definitely pertains to foreign key constraints. See e.g. What does mysql error 1025 (HY000): Error on rename of './foo' (errorno: 150) mean? http://www.xaprb.com/blog/2006/08/22/mysqls-error-1025