Query goal: | Find table columns and domains with the default value that is the empty string or a string that consists of only whitespace (for instance, newlines, spaces). |
Query type: | Problem detection (Each row in the result could represent a flaw in the design) |
Query reliability: | Medium (Medium number of false-positive results) |
Query license: | MIT License |
Fixing suggestion: | If a textual value can be missing, then perhaps it is better to permit NULLs in the column. If the column or domain has NOT NULL constraint, then drop the NOT NULL constraint and the default value. If the column or domain does not have the NOT NULL constraint, then drop the default. |
Data source: | INFORMATION_SCHEMA only |
SQL query: | Click on query to copy it
WITH columns AS (SELECT A.table_schema AS schema, A.table_name, A.column_name AS object, A.data_type, a.column_default AS default_value, 'COLUMN' AS object_type, is_nullable FROM information_schema.columns A INNER JOIN information_schema.schemata S ON A.table_schema=S.schema_name WHERE A.data_type IN ('character varying','text','character') AND A.column_default~*'^''[[:space:]]*''::' AND (A.table_schema = 'public' OR S.schema_owner<>'postgres') AND (table_schema, table_name) IN (SELECT table_schema, table_name FROM information_schema.tables WHERE table_type='BASE TABLE')), domains AS (SELECT D.domain_schema AS schema, NULL AS table_name, D.domain_name AS object, D.data_type, D.domain_default AS default_value, 'DOMAIN' AS object_type, CASE WHEN NOT EXISTS (SELECT * FROM information_schema.domain_constraints AS dc INNER JOIN information_schema.check_constraints AS chk USING (constraint_schema, constraint_name) WHERE D.domain_schema=Dc.domain_schema AND D.domain_name=Dc.domain_name AND chk.check_clause~*'IS NOT NULL')=TRUE THEN 'YES' ELSE 'NO' END AS is_nullable FROM information_schema.domains D INNER JOIN information_schema.schemata S ON D.domain_schema=S.schema_name WHERE D.data_type IN ('character varying','text','character') AND D.domain_default~*'^''[[:space:]]*''::' AND (D.domain_schema = 'public' OR S.schema_owner<>'postgres')) SELECT schema, table_name, object, object_type, data_type, CASE WHEN default_value ~* '^''''::' THEN 'Column default is the empty string' WHEN default_value ~* '^''[[:space:]]+''::' THEN 'Column default consists of whitespace' END AS column_default, is_nullable FROM columns UNION SELECT schema, table_name, object, object_type, data_type, CASE WHEN default_value~* '^''''::' THEN 'Domain default is the empty string' WHEN default_value ~* '^''[[:space:]]+''::' THEN 'Domain default consists of whitespace' END AS domain_default, is_nullable FROM domains ORDER BY schema, table_name, object_type, object; |
SQL query | Description |
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SELECT format('ALTER TABLE %1$I.%2$I ALTER COLUMN %3$I DROP DEFAULT;', A.table_schema, A.table_name, A.column_name) AS statements FROM information_schema.columns A INNER JOIN information_schema.schemata S ON A.table_schema=S.schema_name WHERE A.data_type IN ('character varying','text','character') AND A.column_default~*'^''[[:space:]]*''::' AND (A.table_schema = 'public' OR S.schema_owner<>'postgres') AND (table_schema, table_name) IN (SELECT table_schema, table_name FROM information_schema.tables WHERE table_type='BASE TABLE') ORDER BY A.table_schema, A.table_name, A.ordinal_position; | Drop the column default value. |
SELECT format('ALTER DOMAIN %1$I.%2$I DROP DEFAULT;', D.domain_schema, D.domain_name) AS statements FROM information_schema.domains D INNER JOIN information_schema.schemata S ON D.domain_schema=S.schema_name WHERE D.data_type IN ('character varying','text','character') AND D.domain_default~*'^''[[:space:]]*''::' AND (D.domain_schema = 'public' OR S.schema_owner<>'postgres') ORDER BY D.domain_schema, D.domain_name; | Drop the domain default value. |
SELECT format('ALTER TABLE %1$I.%2$I ALTER COLUMN %3$I DROP NOT NULL;', A.table_schema, A.table_name, A.column_name) AS statements FROM information_schema.columns A INNER JOIN information_schema.schemata S ON A.table_schema=S.schema_name WHERE A.data_type IN ('character varying','text','character') AND A.column_default~*'^''[[:space:]]*''::' AND (A.table_schema = 'public' OR S.schema_owner<>'postgres') AND (table_schema, table_name) IN (SELECT table_schema, table_name FROM information_schema.tables WHERE table_type='BASE TABLE') AND is_nullable='NO' ORDER BY A.table_schema, A.table_name, A.ordinal_position; | Drop the column's NOT NULL constraint. |
SELECT format('ALTER DOMAIN %1$I.%2$I DROP NOT NULL;', D.domain_schema, D.domain_name) AS statements FROM information_schema.domains D INNER JOIN information_schema.schemata S ON D.domain_schema=S.schema_name WHERE D.data_type IN ('character varying','text','character') AND D.domain_default~*'^''[[:space:]]*''::' AND (D.domain_schema = 'public' OR S.schema_owner<>'postgres') AND EXISTS (SELECT * FROM information_schema.domain_constraints AS dc INNER JOIN information_schema.check_constraints AS chk USING (constraint_schema, constraint_name) WHERE D.domain_schema=Dc.domain_schema AND D.domain_name=Dc.domain_name AND chk.check_clause~*'IS NOT NULL') ORDER BY D.domain_schema, D.domain_name; | Drop the domain's NOT NULL constraint. |
Collection name | Collection description |
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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 about integrity constraints | A selection of queries that return information about the state of integrity constraints in the datadabase. 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 . |
Category name | Category description |
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Comfortability of data management | Queries of this category provide information about the means that have been used to make the use or management of database more comfortable and thus, more efficient. |
Default value | Queries of this catergory provide information about the use of default values. |
Missing data | Queries of this category provide information about missing data (NULLs) in a database. |
Validity and completeness | Queries of this category provide information about whether database design represents the world (domain) correctly (validity) and whether database design captures all the information about the world (domain) that is correct and relevant (completeness). |
Reference |
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https://en.wikipedia.org/wiki/Whitespace_character |