Insufficient number of user-defined domains

Query goal:

There must be at least n (one in this case) user-defined domains in the database each of that must be used in case of at least two columns of base tables.

Notes about the query:

This query implements a requirement that might occur in a learning situation. The condition in the query ensures that if the requirement is not fulfilled, then the query returns one row, otherwise it does not return a row. The result is achieved by using a PostgreSQL feature that permits SELECT statements without the FROM clause. The number of domains (one in this case) serves here as an example. It could be replaced with some other threshold.

Query type:

Problem detection (Each row in the result could represent a flaw in the design)

Query reliability:

High (Few or no false-positive results)

Query license:

MIT License

Fixing suggestion:

Create additional domains and use these to define columns of base tables.

Data source:

INFORMATION_SCHEMA only

SQL query:

Click on query to copy it

WITH domains AS (SELECT domain_schema, domain_name
FROM Information_schema.domains AS d
WHERE domain_schema NOT IN (SELECT schema_name
FROM INFORMATION_SCHEMA.schemata
WHERE schema_name<>'public' AND
schema_owner='postgres' AND schema_name IS NOT NULL)
AND (SELECT Count(*) FROM Information_schema.columns AS c INNER JOIN Information_schema.tables AS t USING (table_schema, table_name) WHERE d.domain_schema=c.domain_schema AND d.domain_name=c.domain_name AND t.table_type='BASE TABLE')>=2)
SELECT 'Too few domains that are used in case of at least two columns of base tables, must be at least one' As comment, (SELECT Count(*) AS cnt FROM domains) AS number_of_domains
WHERE (SELECT Count(*) AS cnt FROM domains)<1;

Collections where the query belongs to

Collection name	Collection description
Find problems automatically	Queries, that results point to problems in the database. Each query in the collection produces an initial assessment. However, a human reviewer has the final say as to whether there is a problem or not .

Collection name

Collection description

Find problems automatically

Queries, that results point to problems in the database. Each query in the collection produces an initial assessment. However, a human reviewer has the final say as to whether there is a problem or not .

Categories where the query belongs to

Category name	Category description
Assessment	Queries of this category could be used specifically in the learning environment to assess as to whether student projects have filled certain criteria.
Comfortability of database evolution	Queries of this category provide information about the means that influence database evolution.
Domains	Queries of this category provide information about reusable specifications of column properties.

Category name

Category description

Assessment

Queries of this category could be used specifically in the learning environment to assess as to whether student projects have filled certain criteria.

Comfortability of database evolution

Queries of this category provide information about the means that influence database evolution.

Domains

Queries of this category provide information about reusable specifications of column properties.