A declarative mechanism such as a check or foreign key that enforces some data integrity rule in a database.

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26 views

Assign value to a field after checking a condition

I have this query: ALTER TABLE MERCHANTS ADD COLUMN merchant_image bytea, ADD COLUMN merchant_logo bytea, ADD COLUMN merchant_address VARCHAR(100), ADD COLUMN merchant_phone VARCHAR(50), ...
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1answer
1k views

How to set unique columns combination

see this table: CREATE TABLE IF NOT EXISTS `default_messages_users` ( `id` int(11) NOT NULL AUTO_INCREMENT, `message_id` int(11) NOT NULL, `owner_user_id` int(11) NOT NULL, `to_user_id` ...
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0answers
13 views

Unique attributes as a group [duplicate]

create table test (a int, b int); I want to make a and b be unique, but as a whole. Example: a b - - 1 1 1 2 - this is ok, because even if the previous entry was 1, the b value is different 2 1 - ...
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1answer
35 views

Duplicate check constraint on multiple tables?

I have an integer value for a data to be included into two or three tables, Say it is part no. The integer value of part no must be between 1 to 8. I want to add that constraint into the tables. ...
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0answers
15 views

How to use Domains in oracle database

I am trying to learn about domains. As far as i understand, domains are user defined "types" that describe restrictions of its value. But how would i assign and use a domain in a given table in an ...
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4answers
447 views

Entity relationship problem

I have 4 tables related like this (it's an example): Company: ID Name CNPJ Department: ID Name Code ID_Company Classification: ID Name Code ID_Company Workers: Id Name Code ID_Classification ...
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1answer
47 views

Constrain/limit certain records in sql table definitions

Let's say I have posts on which users can leave a comment. And I want to limit the amount of comments to a certain post to 10, is it possible to add such constraint/restriction to the table? My guess ...
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2answers
523 views

Performance of single vs multiple column unique constraint

I'm using PostgreSQL 9.3. I want to understand if I have an option to make a constraint unique across the entire table vs. unique across a subset of the table (i.e. by using 2 columns in the unique ...
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1answer
52 views

Indirect constraints (foreign keys amongst three/four tables) [duplicate]

I have the next layout of tables: table COMPANY: - primary key pk_company table USERS: - primary key pk_users, - foreign key (fk_company) references COMPANY (pk_company) table GROUPS: <br> - ...
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1answer
158 views

Constrains relationship

I have the following design. Each user has it's own contacts, it's own hosts and assign those to a domain which belongs only to him. I want to insure that the host you assign to the domain belongs ...
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3answers
348 views

Constraint to enforce “at least one” or “exactly one” in a database

Say we have users and each user can have multiple email addresses CREATE TABLE emails ( user_id integer, email_address text, is_active boolean ) Some sample rows user_id | ...
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2answers
663 views

Conditional Foreign Key Relationship

I currently have a foreign key between two entities, and I would like to make that relation conditional to the entityType of one of the tables. Here's the hierachy of tables, this is done via FK ...
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1answer
29 views

Can I enforce one field being dependent on another?

I would like to know if it's possible to have two fields (in this case bits) in the same table where one is dependent on another. For example Check2 may only be true if Check1 is true. Note: I'm ...
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2answers
4k views

How can I help SQL Server recognize my indexed view column is NOT NULL-able?

I have the following indexed view defined in SQL Server 2008 (you can download a working schema from gist for testing purposes): CREATE VIEW dbo.balances WITH SCHEMABINDING AS SELECT user_id ...
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1answer
64 views

Enforce a single NULL end date per foreign key value using an index

I want to implement a Check Constraint across a date range and foreign key. I have a table created as: Primary Key Foreign Key DateStart DateEnd The ForeignKey can appear many times in the table ...
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1answer
46 views

Using REGEX_LIKE to Implement a Check Constraint

Background I am working on the database design for an application that tracks information about database development projects at my company. The project management office (PMO) assigns a ...
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1answer
95 views

Create an “int” column forced between 0 and 3

I would like to create a table with one column that would be of type "integer", and locked between 0 and 3. Is this possible? My goal would be to have this column so that I could just execute a ...
1
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1answer
589 views

Adding foreign keys constraint on databases used

We have a server with about 20 databases, all duplicates of the same original db, and we just noticed the original is missing all the foreign keys constraint for some unknown reason. So of course all ...
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1answer
417 views

How to enforce a constraint over multiple tables?

I have the following five tables: PRODUCT FEATURE PROVIDER PROVIDER_PRODUCT PROVIDER_FEATURE The logic is as follows: A generic PRODUCT can have one or more FEATUREs. There are different ...
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1answer
153 views

Enabling Constraint Silently Fails

Why would SQL Server silently fail to re-enable a foreign key constraint? I recently attempted to re-enable a number of constraints using ALTER TABLE. Most enabled successfully; however, minority of ...
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1answer
81 views

Can Indexes mitigate untrusted Constraint

I using sp_blitz and found two tables that have foreign keys that is untrusted. tried to enable the trust with: ALTER TABLE MyTableName WITH CHECK CHECK CONSTRAINT MyConstraintName; GO But got this ...
3
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3answers
164 views

Cap on number of rows matching a condition in Postgres

Say I have a db schema like this user_id text photo_id text date_created timestamp and I want to enforce a constraint that says "a user can only have 30 photos". A naive way to implement this would ...
0
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1answer
58 views

Is unique index combined with a “not null” constraint equivalent to a PK constraint?

I have these legacy table definitions (from here): CREATE TABLE [dbo].[JobItems] ( [ItemId] UNIQUEIDENTIFIER NOT NULL, -- lots of other columns CONSTRAINT [PrimaryKey_GUID_HERE] ...
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1answer
158 views

Foreign Key Constraint over two tables

I am trying to put the following entity-model into practice: We have a list of Payments, each Payment belongs to a certain store and is of a certain payment type (e.g. 10€ maintenance cost in ...
2
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1answer
173 views

Multi-column uniqueness constraint, checking a field has one of two values

I'd like to enforce that only one row in a database matches value A in column 1, and either value B or value C in column 2. A small example create table builders ( id text serial ); create table ...
3
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1answer
478 views

Postgres 9.3 - deletes terribly slow for 10 minutes after dropping indexes/constraints

If I run a script which drops indexes (17 of them, CONCURRENTLY makes no difference except that without it I get the occasional deadlock), then constraints (20 constraints on 18 tables) and then run a ...
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73 views

MariaDB error on alter table - table removed - constraint name is blocked

Today, we experienced a strange behavior in 5.5.41-MariaDB (InnoDB): An ALTER TABLE (add constraint) statement failed with error (mysql server has gone away after that). Then the database table ...
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1answer
25 views

Verify conditions before creating a constraint

I've taken over an application database that has been grown from an Access db. As such, the database is in need of some significant refactoring. The first step that I'm planning is adding a number of ...
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2answers
36 views

Basic SQL question about setting constraints

In code such as the following, what is the need to write constraint pk_dept primary key (deptno) if just simply primary key (deptno) works? Is pk_dept something the database uses internally, since it ...
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1answer
449 views

Can't add a foreign key constraint in a table on Postgresql

I'm trying to add a foreign key of "prefectures" table in "centresdevote" table. But I'm having this error while trying to add a foreign key to "centresdevote" table. I had no problem adding foreign ...
2
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1answer
47 views

Detect circular relations in a distribution table

I have the following two tables, that will define distribution rates from items on table A to other items on table A (I think I can say B defines a many-to-many relationship for A with itself). ...
11
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2answers
7k views

What does 'ibfk' stand for in MySQL?

If I create a foreign key constraint for table 'photos' in phpmyadmin, I later see that the constraint is named 'photos_ibfk_1', and the next constraint is called 'photos_ibfk_2', etc. From this I ...
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1answer
73 views

SQL Server transactional replication issue with database

We have on the server a database and we want to replicate a database on another server. we've set a transactional replication, but we have issues with the default constraints on the tables: On the ...
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23 views

SQLITE Foreign key has to be re-added? [closed]

Currently I have a mysql database on my computer which I convert to sqlite database. On the sqlite database, I have transaction_detail table with a foreign key to transaction_master table. The ...
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1answer
6k views

PostgreSQL EXCLUDE USING error: Data type integer has no default operator class

In PostgreSQL 9.2.3 I am trying to create this simplified table: CREATE TABLE test ( user_id INTEGER, startend TSTZRANGE, EXCLUDE USING gist (user_id WITH =, startend WITH &&) ); ...
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149 views

What order do foreign key constraints run in? Why does my foreign key not work after import?

I have two tables tags and tag_memberships in a PostgreSQL database. On the tag_memberships table, I have two constraints. The first is this: ALTER TABLE tag_memberships ADD CONSTRAINT ...
2
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1answer
63 views

Can column uniqueness be commutative?

I have a table in a Postgres DB where col1 and col2 are foreign keys referring to the same column. I want only unique combinations of (col1, col2), i.e. if (1,2) is entered then (2,1) should be ...
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3answers
2k views

check key if exists in other table without fk constraint

Lets say i have: table a (id_a int); table b (id_b int, id_a int); I want to check if b.id_a exists in "a" before a new row in "b" will be inserted. Normally I would just add a fk constraint on ...
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1answer
98 views

How can we drop a constraint without losing the automatically created index?

How can we drop a constraint without losing the automatically created index? If it's possible using a single query.
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1answer
755 views

Deferrable Foreign Key Constraints

What are the consequences of making a foreign key constraint DEFERRABLE INITIALLY IMMEDIATE instead of NONDEFERRABLE? This answer on StackOverflow mentions the performance impact that comes with no ...
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0answers
47 views

Compound key that only allows nulls if they are null in the referenced table

I want to create a compound foreign key constraint that only allows a null value in one of the columns if there is a matching row with a null value in the referenced table. Additionally, the ...
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0answers
94 views

Cleaning up orphaned metadata in information_schema

OK - so the server (Percona 5.6 in this case) 'went away' in the middle of declaring a constraint like so: alter table mytable add constraint fk_mytable_myothertable foreign key (myothertable_id) ...
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2answers
135 views

In mysql, find all instances of a named column that are not foreign keys

This one has had me trumped for a while! I want to run a query to retrieve all instances of a column (from information_schema, I guess) that ARE or ARE NOT foreign keys. Now, let me back of a little ...
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1answer
479 views

Postgres - copy table INCLUDING CONSTRAINT doesn't include constraint

How come that statement don't copy constraints if I explicitly ask for it? CREATE TABLE backup_schema.permissions (LIKE public.permissions INCLUDING DEFAULTS INCLUDING CONSTRAINTS INCLUDING INDEXES ...
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1answer
355 views

trigger or check constraint insert values based upon existence of others

For simplicity (and since it captures the essence of my problem), suppose I have a table with data. CREATE TABLE my_practice_table ( my_id NUMBER(12), field_2 VARCHAR2(20), field_3 ...
0
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1answer
49 views

Creating a constraint

I created a report that records entries from a table which has 4 columns 1 Shipper ID 2 SHipper Reference 3 loading 4 Completion My primary keys are columns 1 and 2 there are no foriegn keys, ...
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2answers
474 views

Unique across tables

I have a table containing users. Each user has a primary email and a flag indicating if the user is deleted or not (we never hard-delete users). However, each user can also have additional emails. ...
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55 views

Constraints on a junction table of many entity types?

Let's say I have the following database table and columns: Event: event_id, event_name School: school_id, school_name Automobile: automobile_id, automobile_name User: user_id, username ...
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1answer
859 views

Enforce a column as unique based on another column value

I want to make a column unique, but only if a different column is a specific value. Consider the following table: CREATE TABLE [SampleTable] ( [Id] INTEGER NOT NULL IDENTITY(1,1) ...
0
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1answer
68 views

What does a CONSTRAINT have to do with my unique index?

I have to indexes on my table. The first was created by Django and the second by me. I'm not completely certain what the extra CONSTRAINT means in the first index and am wondering how I would change ...