11/5/2020 Generate Unique Key In Sql
Apr 20, 2006 In SQL terms, a candidate key is any combination of columns that uniquely identifies a row (SQL and the relational model arenât the same thing, but Iâll put that aside for this article). The dataâs primary key is the minimal candidate key. Many people think a primary key is something the DBA defines, but thatâs not true. Feb 23, 2010 The key to generating large number of random and unique alpha numeric code is to generate all of it in one go. Store all the codes in a file or a table and server the requested amount of codes whenever required from there. The SQL script below will generate 10 digit or rather 10 character.
APPLIES TO: SQL Server 2016 and later Azure SQL Database Azure Synapse Analytics (SQL DW) Parallel Data Warehouse
You can create a unique constraint in SQL Server 2019 (15.x) by using SQL Server Management Studio or Transact-SQL to ensure no duplicate values are entered in specific columns that do not participate in a primary key. Creating a unique constraint automatically creates a corresponding unique index.
Note
See Primary key, foreign key, and unique key in Azure Synapse Analytics for information on unique constraints in Azure Synapse Analytics.
In This Topic
Before You BeginSecurityPermissions
Requires ALTER permission on the table.
Using SQL Server Management StudioTo create a unique constraint
Generate Unique Key In Sql TutorialUsing Transact-SQLTo create a unique constraint
To create a unique constraint on an existing table
To create a unique constraint in an new table
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APPLIES TO: SQL Server Azure SQL Database Azure Synapse Analytics (SQL DW) Parallel Data Warehouse
This topic describes how to create a unique index on a table in SQL Server 2019 (15.x) by using SQL Server Management Studio or Transact-SQL. A unique index guarantees that the index key contains no duplicate values and therefore every row in the table is in some way unique. There are no significant differences between creating a UNIQUE constraint and creating a unique index that is independent of a constraint. Data validation occurs in the same manner, and the query optimizer does not differentiate between a unique index created by a constraint or manually created. However, creating a UNIQUE constraint on the column makes the objective of the index clear. For more information on UNIQUE constraints, see Unique Constraints and Check Constraints.
When you create a unique index, you can set an option to ignore duplicate keys. If this option is set to Yes and you attempt to create duplicate keys by adding data that affects multiple rows (with the INSERT statement), the row containing a duplicate is not added. If it is set to No, the entire insert operation fails and all the data is rolled back.
Note
You cannot create a unique index on a single column if that column contains NULL in more than one row. Similarly, you cannot create a unique index on multiple columns if the combination of columns contains NULL in more than one row. These are treated as duplicate values for indexing purposes.
In This Topic
Generate Unique Key In Sql ServerBefore You BeginBenefits of a Unique Index
Typical Implementations
Unique indexes are implemented in the following ways:
Limitations and Restrictions
SecurityPermissions
Requires ALTER permission on the table or view. User must be a member of the sysadmin fixed server role or the db_ddladmin and db_owner fixed database roles.
Using SQL Server Management StudioTo create a unique index by using the Table Designer
Create a unique index by using Object ExplorerGenerate Unique Key In Sql Download
Using Transact-SQLGenerate Unique Key In Sql TutorialTo create a unique index on a table
For more information, see CREATE INDEX (Transact-SQL).
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