Find optional base table columns that participate in a UNIQUE constraint or index but do not participate in a foreign key constraint. Each base table has one or more candidate keys. One of these is usually selected to be the primary key, other are called alternate keys. To enforce an alternate key one should define a UNIQUE constraint and determine that all the key columns are mandatory (NOT NULL) just like the primary key columns are mandatory. Make sure that the NOT NULL constraint is not missing on these columns.
Type
Problem detection (Each row in the result could represent a flaw in the design)
WITH unique_columns AS (SELECT
n.nspname AS table_schema,
c2.relname AS table_name,
a.attname AS column_name
FROM
pg_catalog.pg_class AS c INNER JOIN pg_catalog.pg_index AS i ON i.indexrelid = c.oid
INNER JOIN pg_catalog.pg_class AS c2 ON i.indrelid = c2.oid
INNER JOIN pg_catalog.pg_namespace AS n ON c.relnamespace = n.oid
INNER JOIN pg_catalog.pg_authid AS u ON n.nspowner = u.oid
INNER JOIN pg_catalog.pg_attribute AS a ON a.attrelid = c.oid
WHERE c.relkind = 'i'
AND i.indisunique=TRUE
AND a.attnum>=1
AND a.attisdropped = FALSE
AND (n.nspname = 'public'
OR u.rolname <> 'postgres')),
fk as (select
(select nspname from pg_namespace where oid=c.relnamespace) as target_schema,
c.relname as target_table,
c.oid as target_table_oid,
o.conkey AS target_col
from pg_constraint o inner join pg_class c on c.oid = o.conrelid
where o.contype = 'f'),
fk_unnest as (select target_schema, target_table, target_table_oid, target_col, target_col_num, ordin
from fk, unnest(fk. target_col) with ordinality as f(target_col_num, ordin)),
fk_with_names as (select target_schema, target_table, a_target.attname as target_col
from fk_unnest fk inner join pg_attribute a_target on fk.target_col_num = a_target.attnum and fk.target_table_oid = a_target.attrelid and a_target.attisdropped = false)
SELECT A.table_schema, A.table_name , A.column_name, CASE WHEN A.data_type ILIKE 'character%' AND A.character_maximum_length IS NOT NULL THEN A.data_type || '(' || A.character_maximum_length::text || ')'
WHEN A.data_type ILIKE 'timestamp%' AND A.datetime_precision IS NOT NULL THEN A.data_type || '(' || A.datetime_precision || ')'
WHEN A.data_type ILIKE 'numeric%' AND A.numeric_precision IS NOT NULL THEN A.data_type || '(' || A.numeric_precision::text || ',' ||coalesce(A.numeric_scale,0)::text || ')'
WHEN A.data_type ILIKE 'interval%' AND A.interval_type IS NOT NULL THEN A.data_type || '(' || A.interval_type::text || ')'
WHEN A.data_type='USER-DEFINED' THEN A.udt_schema || '.' || A.udt_name
ELSE A.data_type END AS data_type
FROM information_schema.columns A INNER JOIN information_schema.tables T USING (table_schema, table_name)
INNER JOIN information_schema.schemata S ON A.table_schema=S.schema_name
WHERE is_nullable='YES'
AND T.table_type='BASE TABLE'
AND (A.table_schema = 'public'
OR S.schema_owner<>'postgres')
AND (table_schema, table_name, column_name) IN (SELECT table_schema, table_name, column_name
FROM unique_columns)
AND NOT EXISTS (SELECT *
FROM fk_with_names AS fwn
WHERE A.table_schema=fwn.target_schema
AND A.table_name=fwn.target_table
AND A.column_name=fwn.target_col)
ORDER BY table_schema, table_name, ordinal_position;
Collections
This query belongs to the following collections:
Name
Description
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 .
Categories
This query is classified under the following categories:
Name
Description
Missing data
Queries of this category provide information about missing data (NULLs) in a database.
Uniqueness
Queries of this category provide information about uniqueness constraints (PRIMARY KEY, UNIQUE, EXCLUDE) as well as unique indexes.
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).