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An architecture note on why every InnoDB table needs an explicit, monotonically increasing primary key, how the PK shapes clustered and secondary indexes, and practical checks to avoid page‑split storms and replication lag.
Learn how to pick a ClickHouse MergeTree primary key that enables partition pruning and skip indexes, turning slow range scans into fast lookups.
Goal Determine how Zend Framework 2’s Zend_Db_Table::save reacts when a caller supplies a primary‑key value that does not match any existing row, and whether retrying the same operation can create duplicate records. Constraints & Uncertainty Framework 2 documentation specifies that save performs an INSERT if the primary‑key is null or not found, otherwis
Not sure which option is latest best practice? I read on on this tutorial that: https://www.postgresqltutorial.com/postgresql-identity-column/ PostgreSQL version 10 introduced a new constraint GENERATED AS IDENTITY that allows you to automatically assign a unique number to a column. The GENERATED AS IDENTITY constraint is the SQL standard-conforming variant
I created this first table named 'bookstore' where Primary Key is book_name: create table bookstore (book_name varchar primary key, author varchar, price decimal); I am trying to create a second table named 'name' where name is primary key. I want to make this primary key- author.name as a foreign key of bookstore.author. create table author (name varchar pr
Attempting to Modify a Primary Key Column When executing ALTER TABLE t MODIFY COLUMN col TYPE String on a MergeTree‑family table that already defines col in its primary key, ClickHouse throws the error DB::Exception: Cannot alter column 'col' because it is used in the primary key . The operation is rejected before any data mutation occurs. Constraints and Un
Asked · 13 Oct 2022, 05:11 UTC
answered · 16 Oct 2022, 05:11 UTC
mysql
clickhouse
zend
postgresql