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Some database implementations adopted the term upsert (a portmanteau of update and insert) to a database statement, or combination of statements, that inserts a record to a table in a database if the record does not exist or, if the record already exists, updates the existing record. This synonym is used in PostgreSQL (v9.5+) [2] and SQLite (v3 ...
In some databases, such as PostgreSQL, when a FROM clause is present, what essentially happens is that the target table is joined to the tables mentioned in the fromlist, and each output row of the join represents an update operation for the target table. When using FROM, one should ensure that the join produces at most one output row for each ...
For example: GRANT can be used to give privileges to user to do SELECT, INSERT, UPDATE and DELETE on a specific table or multiple tables. The REVOKE command is used to take a privilege away (default) or revoking specific command like UPDATE or DELETE based on requirements.
When an MVCC database needs to update a piece of data, it will not overwrite the original data item with new data, but instead creates a newer version of the data item. Thus there are multiple versions stored. The version that each transaction sees depends on the isolation level implemented.
These features included the ability to define types and to fully describe relationships – something used widely, but maintained entirely by the user. In POSTGRES, the database understood relationships, and could retrieve information in related tables in a natural way using rules. POSTGRES used many of the ideas of Ingres, but not its code. [31]
It maintains database consistency across multiple hardware nodes by replicating transactions in a synchronous manner (two-phase commit). An important characteristic of eXtremeDB Cluster is transaction replication, in contrast to log file-based, SQL statement-based, or other replication schemes that may or may not guarantee the success or ...
Create/alter table: Yes - can create table, alter its definition and data, and add new rows; Some - can only create/alter table definition, not data; Browse table: Yes - can browse table definition and data; Some - can only browse table definition; Multi-server support: Yes - can manage from the same window/session multiple servers
Database-level triggers can help enforce multi-table constraints, or emulate materialized views. If an exception is raised in a TRANSACTION COMMIT trigger, the changes made by the trigger so far are rolled back and the client application is notified, but the transaction remains active as if COMMIT had never been requested; the client ...