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- Dictionaryunique/juːˈniːk/
adjective
- 1. being the only one of its kind; unlike anything else: "this discovery was unique in history" Similar Opposite
noun
- 1. a unique person or thing: archaic "some of Lamb's writings were so memorably beautiful as to be uniques in their class"
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Mar 28, 2018 · In EF Core you could use the extension method HasAlternateKey in fluent API only. There are no data annotations to realize a unique constraint. This MS doc article - Alternate Keys (Unique Constraints) - will explain how to use and which further possibilities are exist. A short example from link above: class MyContext : DbContext.
Since Entity Framework Core (EF Core) 5.0 we can configure Unique Indexes via Data Annotations. It is little different to e.g. EF6, because we cannot set it on the property itself but instead on the class. [Index(nameof(EmailAddress), IsUnique = true)] public class User. [Key] public Guid Id { get; set; }
ADD UNIQUE - to add the unique constraint. You then can define your new unique key with the format 'name'('column1', 'column2'...) For those people using MySQL workbench: go to the Indexes tab and select UNIQUE as your type. Give your index a name and check the appropriate columns under the section "Index Columns".
Sep 19, 2013 · The second approach to create Unique Constraints with EF Core by using Alternate Keys. Examples. One column: Multiple columns: EF 6 and below: First approach: @"CREATE UNIQUE INDEX LX_{0} ON {0} ({1})", "Entitys", "FirstColumn, SecondColumn")); This approach is very fast and useful but the main problem is that Entity Framework doesn't know ...
Nov 27, 2018 · EF doesn't support unique columns except keys. If you are using EF Migrations you can force EF to create unique index on UserName column (in migration code, not by any annotation) but the uniqueness will be enforced only in the database. If you try to save duplicate value you will have to catch exception (constraint violation) fired by the ...
Jun 27, 2010 · Defining Unique Constraints. JPA helps us to achieve that with the @UniqueConstraint annotation. We do that in the @Table annotation under the uniqueConstraints attribute. Let's remember to specify the names of the columns: @Table(uniqueConstraints = { @UniqueConstraint(columnNames = { "personNumber", "isActive" }) })
Feb 13, 2017 · This doesn't work for me. Neither do any of the answers below. I'm trying to run a query equivalent to this: CREATE TABLE scores (id INT PRIMARY KEY NOT NULL, oppId INT NOT NULL, oppType TEXT NOT NULL, tree TEXT NOT NULL, version INT NOT NULL, score JSON NOT NULL, CONSTRAINT uniq_scores UNIQUE(oppId, oppType, tree, version));.
Using the constraints features UniqueConstraint is preferred over unique_together. From the Django documentation for unique_together: Use UniqueConstraint with the constraints option instead. UniqueConstraint provides more functionality than unique_together. unique_together may be deprecated in the future. For example:
Apr 25, 2015 · Primary Key. 1)can't insert null value. 2) one table have one primary key. Unique key 1) insert null value one at time 2)one table have multiple unique key 3) you can refereed as candidate key also. foreign key 1) maintain the relationship between two table and also multiple Note: without any constraint you get data in multiple table but you ...
Once you have removed your duplicate (s): ADD CONSTRAINT uq_yourtablename UNIQUE(column1, column2); or. ON dbo.yourtablename(column1, column2); Of course, it can often be better to check for this violation first, before just letting SQL Server try to insert the row and returning an exception (exceptions are expensive).
