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A foreign key is a set of attributes in a table that refers to the primary key of another table, linking these two tables. In the context of relational databases, a foreign key is subject to an inclusion dependency constraint that the tuples consisting of the foreign key attributes in one relation, R, must also exist in some other (not necessarily distinct) relation, S; furthermore that those ...
SQL allows triggers to fire on updates to specific columns; As of version 9.0 of PostgreSQL this feature is also implemented in PostgreSQL. The standard allows the execution of a number of SQL statements other than SELECT , INSERT , UPDATE , such as CREATE TABLE as the triggered action.
In SQL, the TRUNCATE TABLE statement is a Data Definition Language (DDL) operation that deletes all rows of a table without causing a triggered action. [1] The result of this operation quickly removes all data from a table, typically bypassing a number of integrity enforcing mechanisms.
Transaction log - DELETE needs to read records, check constraints, update block, update indexes, and generate redo / undo. All of this takes time, hence it takes time much longer than with TRUNCATE; reduces performance during execution - each record in the table is locked for deletion; DELETE uses more transaction space than the TRUNCATE statement
Some hospitals in the U.S. are seeing an increase in RSV and higher levels of "walking pneumonia" among young children despite overall respiratory illness activity remaining low nationally.
LONDON/SYDNEY (Reuters) -The U.S. dollar was poised for a big weekly gain on Friday, towering near one-year highs as a hawkish turn from the Federal Reserve chief sent short-term Treasury yields ...
Don't mess with turkeys. That's the lesson we learned after watching some wild turkeys patrol a suburban neighborhood. These birds weren't messing around!
Reserved words in SQL and related products In SQL:2023 [3] In IBM Db2 13 [4] In Mimer SQL 11.0 [5] In MySQL 8.0 [6] In Oracle Database 23c [7] In PostgreSQL 16 [1] In Microsoft SQL Server 2022 [2]