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

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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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Multi-tenant database constraints

I have a multi-tenant app in PostgreSQL that has a repeated tenant_id column in each table to help isolate the tenants from each other. My question is, is there any sort of way that I can use ...
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301 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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Constrain Partial Values in Timestamp

I'm working on a some Create Table statements for a project I have. I have two columns (StartDate, EndDate) where the data type is Timestamp. One of the requirements is to ensure that the date is ...
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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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961 views

User defined table type with a check constraint

I have a user defined table type where I want to make sure that a certain column is within a given range. This range however is defined in another table. So I thought I can use a check constraint on ...
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333 views

postgresql multi column unique or check constraint

First a word of pleading. To say I am a newbie to postgresql would be an insult to the newbies! I have been working on this for only a day or so. I have found several questions on this site, and ...
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89 views

Dealing with Invisible Referencers

Using Oracle database, suppose I have a parent table parent defined in schema A, and a child table child defined in schema B. To achieve this, schema A granted references privilege on parent to schema ...
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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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40 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 ...
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45 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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Is there a workaround for the lack of foreign keys constraint to a partitioned table in PostgreSQL?

I have a big table A (~30 million lines) at the core of my model. Another table B has a foreign key referencing A. I would like to partition A using the well-known inheritance hack. Is there a ...
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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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54 views

Cannot drop constraint in SQL server 2008

When I try to delete a constraint, it gives me the following message: "The constraint is used by merge replication for identity management and cannot be dropped directly. Execute ...
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53 views

Email Column Constraint to Contain '@' character

How do you create an inline constraint for a Email Address Field that requires there be an "@" character? Pretty much I want there to be a restriction to the field so that the data entered must have ...
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43 views

How to combine a default value with a new value?

I need to start the value of a column with CON, so when I insert a new value, it needs to "combine" both default and new value; for example: In the CONTACTO_ASP2_TAB table, the column NOMBRE has to ...
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178 views

cascade delete doesn't work even though constraint is added

I created the following table: CREATE TABLE message_link ( id serial NOT NULL, thread_id integer, message_id integer, user_id integer, read boolean NOT NULL, CONSTRAINT message_link_pkey ...
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57 views

Two different unique constraints for 1 table?

I must enforce uniqueness within my table, But I cannot seem to find anywhere online(mysql manual,forums,stack overflow) talk about two unique constraints within one table. Why you might ask I need ...
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148 views

Error adding constraint foreign key to bridge table

Hi there I am fairly new to sql development. I am current following the head first into mysql book and is on chapter 6. On chapter 6 there is a table in third normal form but it does not contains the ...
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1k views

CHECK constraint ignored during INSERT SELECT

I have the following 2 tables (simplified): CREATE TABLE dbo.[StagingTable] ( HostName [nvarchar] (max) NULL ,UserName [nvarchar] (max) NULL ,AccountType [nvarchar] (max) NULL ) CREATE TABLE ...
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790 views

PostgreSQL Cascade Delete not working

What am I missing here? I have two tables: CREATE TABLE source ( "sourceid" serial, "state" character varying(255) REFERENCES states (state), "leadtime" character varying(255), CONSTRAINT ...
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123 views

Why does mysql show Primary key constraint on a View?

As far as I know views cannot have a primary key. However the result of SELECT FROM KEY_COLUMN_USAGE says differ. PRIMARY | S_MOBILE_ITEM_VIEW | ID | ...