Why is primary key needed in transactional replication? The reason is in the subscriber, rows are updated/deleted one-by-one using primary key. For example: If you delete 100 rows in the publisher using a single DELETE statement, in the subscriber 100 DELETE statements would be executed.
Why is a primary key needed? The main purpose of primary key is to identify the uniqueness of a row, where as unique key is to prevent the duplicates, following are the main difference between primary key and unique key. Primary Key : There can only be one primary key for a table. The primary key consists of one or more columns.
Does snapshot replication require primary key? Snapshot replication does not require a primary key.
Is primary key necessary for every table? Each table should have a primary key. A column or combination of columns that qualify as a primary key value is referred to as a candidate key.”
What is difference between primary key and foreign key? Primary key uniquely identify a record in the table. Foreign key is a field in the table that is primary key in another table. Primary Key can’t accept null values.
Why is primary key needed in transactional replication? – Additional Questions
Do SQL views have primary keys?
Views don’t have primary keys or indexes – the mysql engine will use the indexes and keys defined on the base table(s).
How do you set up merge replication?
Step 1: First you need to initiate the SQL Server and select “replication” under the Configure Distribute options. Step 3: Select a New Publication and specify the database you want. Select “Merge Replication” and set the snapshot to start the process. Step 4: Specify a synchronization schedule.
Can we configure replication in simple recovery model?
Yes, you can use the Simple recovery model the transaction log is only truncated after a checkpoint AND all transaction marked for replication have been processed.
Can a table have 2 primary keys?
No. You cannot use more than 1 primary key in the table. for that you have composite key which is combination of multiple fields.
Can 2 tables have the same primary key?
Yes. You can have same column name as primary key in multiple tables. Column names should be unique within a table. A table can have only one primary key, as it defines the Entity integrity.
Can foreign key be NULL?
By default there are no constraints on the foreign key, foreign key can be null and duplicate. while creating a table / altering the table, if you add any constrain of uniqueness or not null then only it will not allow the null/ duplicate values.
Can foreign key be a primary key?
Foreign keys are almost always “Allow Duplicates,” which would make them unsuitable as Primary Keys. It is perfectly fine to use a foreign key as the primary key if the table is connected by a one-to-one relationship, not a one-to-many relationship.
Can Unique Key be a primary key?
A primary key must be unique. A unique key does not have to be the primary key – see candidate key. That is, there may be more than one combination of columns on a table that can uniquely identify a row – only one of these can be selected as the primary key.
Does foreign key have to be unique?
Any primary key must be unique and non-null. Therefore if the child table has a foreign key referencing the parent’s primary key, it must match a non-null, unique value, and therefore references exactly one row in the parent table. In this case you can’t make a child row that references multiple parent rows.
How do I add a primary key to a view?
You cannot create a primary key on a view. In SQL Server you can create an index on a view but that is different to creating a primary key. If you give us more information as to why you want a key on your view, perhaps we can help with that.
Can views contain primary key and foreign key?
You can specify only unique, primary key, and foreign key constraints on views.
What is primary key in MySQL?
In MySQL, a primary key is a single field or combination of fields that uniquely defines a record. None of the fields that are part of the primary key can contain a NULL value. A table can have only one primary key.
How does merge replication work?
Merge replication allows various sites to work autonomously and later merge updates into a single, uniform result. Because updates are made at more than one node, the same data may have been updated by the Publisher and by more than one Subscriber.
What is the difference between replication and sharding?
What is the difference between replication and sharding?
What are the benefits of peer-to-peer replication?
Because data is maintained across the nodes in near real-time, peer-to-peer replication provides data redundancy, which increases the availability of data. Consider a Web application. This can benefit from peer-to-peer replication in the following ways: Catalog queries and other reads are spread across multiple nodes.
What is replication in genetics?
DNA replication is the process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules. Replication is an essential process because, whenever a cell divides, the two new daughter cells must contain the same genetic information, or DNA, as the parent cell.
Does transactional replication lock tables?
Produces native-mode bulk copy program output of all tables but does not lock tables during the snapshot. Only supported for transactional publications. The native method will bulk copy the data out of SQL Server, but locks the table until the process is complete.
Can a table have 3 primary keys?
A table can only ever have a one primary key. It is not possible to create a table with two different primary keys. You can create a table with two different unique indexes (which are much like a primary key) but only one primary key can exist.
Can a column be a primary and foreign key?
Technically database will not allow you to create a foreign key on same primary key column key. Because foreign key should point to primary key column of another. If foreign key is pointing to same column which has primary key then it will be fail.
Can foreign key be part of composite primary key?
The foreign key can not refer to part of composite primary key of other table. Because it is supposed to be one-to-one relationship and if you refer just part of primary-key, there might be more than one parent record available, which is neither allowed nor possible.