Query Database Information

Suppose we need to ensure everything is organized and optimized in our growing database. To achieve this, quick ways to retrieve structural information about the database itself. This is where learning to query database information becomes incredibly valuable. Querying database information also allows us to uncover insights about the tables, columns, constraints, and other structural elements without directly inspecting the database design.

Let's explore accessing and reviewing critical database metadata. We'll aim to:

• Understand why querying database information is essential for development and maintenance.

• Use SQL commands to view the list of databases and tables.

• Retrieve details about table structures and columns.

Accessing database metadata

Metadata provides descriptive information about the data stored in a database, such as table names, column details, and constraints. Accessing metadata is crucial for database management and often helps in debugging or enhancing performance. Having quick and straightforward queries to gather this information makes our workflow smoother.

The INFORMATION_SCHEMA is a standard SQL schema that contains views providing information about the database. These views include details about tables, columns, constraints, and more. It is like a dictionary of the database. Common INFORMATION_SCHEMA views are:

• SCHEMATA: Information about all databases.

• TABLES: Lists all tables in the database.

• COLUMNS: Provides information about columns in a table.

• TABLE_CONSTRAINTS: Details about table constraints (e.g., primary keys).

• KEY_COLUMN_USAGE: Information about key constraints.

Let's take a closer look at the usage of each of the above-listed views.

Listing all databases

To list all databases, we use the SCHEMATA as follows:

The query above retrieves a list of all database names on the ...