PostgreSQL is one of the latest database engines developed by volunteers from around the world. Most SQL databases are expensive, complicated or both. The PostgreSQL database engine attempts to make managing a SQL server easy, and it’s open source so anyone can contribute to the project. When software is open source, you have the ability to contribute to its functionality. The idea is that the software manifests into a useful tool that not only takes user input and feedback, but that feedback is incorporated by users themselves.
When you install the software and start making databases, you won’t be able to keep track of the database and the tables associated within the database. To give you a way to view all tables associated with a database, the PostgreSQL database engine has functionality that lets you view all tables created in the database. Of course, you need the proper permissions to view the list, but most users have access to at least read the list of tables.
What are Tables?
If you’re new to databases and database design, you must understand the way a database is laid out in a basic layout. Databases are installed and executed from a database server. Databases (especially on busy servers) take up a lot of resources on a server, so your database server must have plenty of memory, CPU power and fast hardware to keep up with user demands.
The database engine runs on our server, and it keeps your users tables. You can run several databases on one database server. You can think of a database as a container for tables. The database also contains the security permissions, the stored procedures, table layout and relationships, and the indexes programmed on your tables. Databases are separate entities from each other, but you can program your one database to access another on the same server or on a different server.
Tables are the entities that contain all of your data. Tables are segmented into rows and columns. The columns define the type of data recorded in each field, and a row represents one record. You can have millions of records in one table. However, if your database is poorly designed, you will have severe performance issues as the tables’ amount of records increases.
You can have hundreds of tables contained in one database, which is why you need some kind of command to view a list of tables when you need to review and audit the database objects. Some tables can be archived, and you don’t realize you don’t use them until you see a list of tables and audit your software to see what tables are needed. You might also need to see table names and indexes to make sure your database is designed with the best performance in mind.
Viewing a List of Tables in PostgreSQL
First, if you can’t remember your database names, you can use the PostgreSQL “/list” command to view a list of databases. You can also use SQL to view a list of databases. The following command displays a list of databases in your database server:
SELECT datname FROM pg_database ORDER BY datname
Once you find the database you want to view, you can view a list of tables. To connect to a database from the PostgreSQL command line, use “/c database_name” in your command line. Replace “database_name” with the name of your database. You will be prompted for a user name and password if you do not have permissions with the current user account. It’s best to list databases and tables with the system administrator account to ensure that you can view your database objects without being filtered by permission levels.
If you have the database open and active, you can use the simple PostgreSQL command “/dt” to view a list of tables. However, you can also use the SQL language to get a list of tables in the database. The following code displays a list of tables in a specific database:
SELECT table_schema, table_name FROM information_schema.tables WHERE table_type = ‘BASE TABLE’
The code above displays a list of tables in a database. The “base table” parameter in the where clause excludes system tables from the list. You can also order your list of tables using the following code:
SELECT table_schema, table_name FROM information_schema.tables WHERE table_type = ‘BASE TABLE’ ORDER BY table_name
There may be times that you want to view system tables. For instance, if you’re having issues with your database, you might think that a system table is corrupted, or you might want to check that the table is available and not causing problems with your applications. The following code lets you see a list of your system tables, which are important for the PostgreSQL database engine to execute queries:
SELECT * FROM pg_catalog.pg_tables ORDER BY table_name
After you’ve seen your list of tables, you can use this view to audit tables, users and permissions. Viewing the tables also gives you a good idea of the relationships and types of data you store in your database.
PostgreSQL is not the most popular database engine, but it helps to know the different engines on the market if you want to be diverse in your database skills. This type of question is typically in technical interviews, so now you can answer questions regarding table lists for PostgreSQL, which some companies use in enterprise applications.