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Base tables with exactly one key

Query goal: Find all base tables that have exactly one PRIMARY KEY or UNIQUE constraint. Find and enforce all the keys. Are you sure there are not more keys in the table?
Notes about the query: PostgreSQL 14 added primary keys, unique constraints, and foreign keys to system catalogs. Thus the query was modified to exclude the results from the system catalog.
Query type: General (Overview of some aspect of the database.)
Query license: MIT License
Data source: system catalog only
SQL query: Click on query to copy it

with keys as (select 
o.conname, 
nc.nspname as key_schema,
c.relname as key_table, 
c.oid as key_table_oid,
o.conkey AS key_col,
case when o.contype='p' then 'PRIMARY KEY' ELSE 'UNIQUE' END as contype
from pg_constraint o inner join pg_class c on c.oid = o.conrelid
inner join pg_namespace as nc on nc.oid=c.relnamespace
inner join  pg_authid AS a on nc.nspowner=a.oid
where (nc.nspname='public' or rolname<>'postgres')
and o.contype in ('u', 'p')),
keys_unnest as (select conname, key_schema, key_table, key_table_oid, key_col, key_col_num, ordin, contype
from keys, unnest(keys.key_col) with ordinality as k(key_col_num, ordin)),
keys_with_names as (select conname, key_schema, key_table, contype, string_agg(a_key.attname,',' order by ordin) as key_col
from keys_unnest k inner join pg_attribute a_key on k.key_col_num = a_key.attnum and k.key_table_oid = a_key.attrelid and a_key.attisdropped = false
group by conname, key_schema, key_table, contype)
select key_schema, key_table, string_agg(contype,',') AS contype, string_agg(key_col,',') AS key_col 
from keys_with_names
group by key_schema, key_table
having count(*)=1
order by key_schema, key_table;

Collections where the query belongs to

Collection nameCollection description
Find problems by overviewQueries that results point to different aspects of database that might have problems. A human reviewer has to decide based on the results as to whether there are problems or not .

Categories where the query belongs to

Category nameCategory description
UniquenessQueries of this category provide information about uniqueness constraints (PRIMARY KEY, UNIQUE, EXCLUDE) as well as unique indexes.
Validity and completenessQueries 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).

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