Goal The choice of data types should reveal as much as possible about the nature of the data in the column. The type of these columns could be CHAR(1) and they should have a constraint that a value in the column cannot be an empty string.
Notes Query returns also information about columns that properties have been specified through a domain.
Type Problem detection (Each row in the result could represent a flaw in the design)
Reliability Medium (Medium number of false-positive results)
License MIT (opens in new tab)
Fixing Suggestion Change the type of the column and add the constraint.
Data Source INFORMATION_SCHEMA only
SQL Query 
SELECT table_schema, table_name, column_name
FROM INFORMATION_SCHEMA.columns
WHERE (table_schema, table_name) IN (SELECT table_schema, table_name
FROM INFORMATION_SCHEMA.tables WHERE table_type='BASE TABLE') AND 
table_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 data_type = 'character varying' AND 
character_maximum_length=1
ORDER BY table_schema, table_name, ordinal_position;

Collections

This query belongs to the following collections:

Find problems about base tables

A selection of queries that return information about the data types, field sizes, default values as well as general structure of base tables. Contains all the types of queries - problem detection, software measure, and general overview

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 .

NameDescription
Find problems about base tablesA selection of queries that return information about the data types, field sizes, default values as well as general structure of base tables. Contains all the types of queries - problem detection, software measure, and general overview
Find problems automaticallyQueries, 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

This query is classified under the following categories:

Data types

Queries of this category provide information about the data types and their usage.

NameDescription
Data typesQueries of this category provide information about the data types and their usage.

Further reading and related materials:

Factor, P.: SQL Code Smells. Redgate, http://assets.red-gate.com/community/books/sql-code-smells.pdf last accessed 2024/12/24 (Using VARCHAR(1), VARCHAR(2), etc).
Reference
Factor, P.: SQL Code Smells. Redgate, http://assets.red-gate.com/community/books/sql-code-smells.pdf last accessed 2024/12/24 (Using VARCHAR(1), VARCHAR(2), etc).