When designing an SQL database, there may be cases where you want to impose restrictions on what data can be added to certain columns in a table. SQL makes this possible through the use ofconstraints. After app
REFERENCES: value must exist in a column in another table After the columns are defined, table-wide constraints may be declared. Table-wide constraints can be either UNIQUE, PRIMARY KEY, CHECK, or REFERENCES. How to Create a Table in PostgreSQL Let's create a test table to pract...
$ su - postgres $ psql -c "select client_addr,sync_state from pg_stat_replication;" If no errors are observed, go ahead and stop the DB on all nodes, ahead of cluster configuration: Run from all nodes aspostgresuser to stop the database and replication: ...
The query is then transformed into a query plan by the optimizer, which evaluates various strategies in order to determine the most efficient approach based on database statistics, indexes, and constraints. This plan then becomes a detailed blueprint outlining how PostgreSQL will access and...
PostgreSQL does not provide any direct command or function to disable / enable the Foreign key constraints. When you create any Foreign Key on the table, internally It creates a hidden trigger for check data integrity. You should enable/disable the trigger for achieving dis...
To dump a single table, use the -t option: pg_dump -t table_name database_name > table.sql In this case, pg_dump will not dump any other database objects linked to the selected table. It means that there is no guarantee that you will be able to restore this dump on a clean dat...
The easiest way to check this is to query the REST API on the web server at `/health/`; this will return a JSON object that can be parsed to determine whether components are healthy and, if not, when they were last seen.SchedulerThis component needs to be running and working ...
OpenPSQL shell(a feature on preview) is a terminal based front-end to PostgreSQL that enables you to type in queries interactively, issue them to PostgreSQL, and see the query results. With this feature, you don't need to copy your connection strings to connect. T...
In this first part, we will set up replication using repmgr and register all the nodes. We will see how to check the status of the whole cluster using a simple command. In the second part, we will simulate a primary node failure and see how the repmgr daemon can automatically sense the...
In Postgres Delete Cascade, we will learn how to manage database CRUD operation delete in case of a relational database that contains multiple tables with foreign key constraints between them. When deleting records from a table in PostgreSQL, it is crucial to consider whether it has any foreign...