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Incorrect check of NULLs

Query goal: Find the use of =NULL and <>NULL in case of table level check constraints, domain level check constraints, WHEN clauses of triggers, WHERE clauses of rules, subqueries of derived tables, and bodies of routines. Write correct code. In order to determine as to whether a value is missing or not one has to use the IS [NOT] NULL predicate. NULL is the marker in SQL that denotes a missing value. Although it is often called "NULL value", one cannot treat it as an ordinary value, i.e., use it in comparisons as a value.
Notes about the query: The query does not consider the routines that are a part of an extension. In the returned body of routine and subquery of view/materialized view the query replaces each newline character with the line break (br) tag for the better readability in case the query result is displayed in a web browser. There could be multiple routines with the same name but with different parameters in the same schema (overloading). Thus, for the unique identification of the routine it is necessary to present also its parameters in addition to the schema name and routine name. The query tries to exclude UPDATE statements (e.g., UPDATE x SET y=NULL).
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: Use IS NOT NULL predicate instead of <>NULL. Use IS NULL predicate instead of =NULL.
Data source: INFORMATION_SCHEMA+system catalog
SQL query: Click on query to copy it

WITH expressions AS (select 
n.nspname as schema,
c.relname || '.' || o.conname as name, 
substring(pg_get_constraintdef(o.oid),7) as expression,
'TABLE CHECK' AS type
from pg_constraint o inner join pg_class c on c.oid = o.conrelid
inner join pg_namespace n on n.oid=c.relnamespace
where o.contype ='c'
and n.nspname not in (select schema_name
from information_schema.schemata
where schema_name<>'public' and
schema_owner='postgres' and schema_name is not null)
union select n.nspname as schema,
t.typname || '.' || o.conname as name, 
substring(pg_get_constraintdef(o.oid),7) as expression,
'DOMAIN CHECK' AS type
from pg_constraint o inner join pg_type t on t.oid = o.contypid
inner join pg_namespace n on n.oid=t.typnamespace
where o.contype ='c' and n.nspname not in (select schema_name
from information_schema.schemata
where schema_name<>'public' and
schema_owner='postgres' and schema_name is not null)
UNION SELECT trigger_schema, event_object_table || '.' || trigger_name, action_condition, 'TRIGGER WHEN' AS type
FROM INFORMATION_SCHEMA.triggers
WHERE action_condition IS NOT NULL
UNION SELECT schemaname, tablename || '.' || rulename, definition, 'RULE WHERE' AS type
FROM pg_catalog.pg_rules
WHERE schemaname NOT IN (SELECT schema_name
FROM INFORMATION_SCHEMA.schemata
WHERE schema_name<>'public' AND
schema_owner='postgres' AND schema_name IS NOT NULL)
UNION SELECT table_schema, table_name, view_definition, type
FROM (SELECT  table_schema, table_name, regexp_replace(view_definition,'[\r\n]','<br>','g') AS view_definition, 'VIEW SUBQUERY' AS type
FROM information_schema.views
WHERE 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)
UNION SELECT schemaname, matviewname, regexp_replace(definition,'[\r\n]','<br>','g') AS definition, 'MATERIALIZED VIEW SUBQUERY' AS type
FROM pg_catalog.pg_matviews) AS foo
WHERE view_definition ~*'^.+([[:space:]]+where[[:space:]]+|[[:space:]]+having[[:space:]]+).+$'
UNION SELECT pg_namespace.nspname AS routine_schema,  pg_proc.proname || '(' || pg_get_function_identity_arguments(pg_proc.oid)  || ')' AS routine_name,  regexp_replace(pg_proc.prosrc,'[\r\n]','<br>','g')  AS routine_src, 'ROUTINE BODY' AS type
FROM pg_catalog.pg_proc, pg_catalog.pg_namespace
WHERE pg_proc.pronamespace = pg_namespace.oid AND
pg_proc.proname NOT IN ('f_assume_you_must_use_files', 'f_check_format_comma_separated_list', 'f_check_password', 'f_default_value_with_no_match') AND 
pg_namespace.nspname NOT IN (SELECT schema_name
FROM INFORMATION_SCHEMA.schemata
WHERE schema_name<>'public' AND
schema_owner='postgres' AND schema_name IS NOT NULL) AND NOT EXISTS (SELECT 1
FROM pg_catalog.pg_depend d 
WHERE EXISTS (SELECT 1 FROM pg_catalog.pg_extension e WHERE d.refobjid=e.oid) AND
d.objid=pg_proc.oid))
SELECT schema, name AS object_identifier, type AS object_type, expression AS suspected_expression
FROM expressions
WHERE expression ~*'^.*((<>|!=)[[:space:]]*NULL([[:space:]]+|::)|(?<!update[^;]*)=[[:space:]]*NULL([[:space:]]+|::)|NULL([[:space:]]*|::)(<>|!=)|NULL([[:space:]]*|::)=).*$'
ORDER BY schema, type, name;

Collections where the query belongs to

Collection nameCollection description
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 where the query belongs to

Category nameCategory description
CHECK constraintsQueries of this category provide information about CHECK constraints.
Derived tablesQueries of this category provide information about the derived tables (views, materialized views), which are used to implement virtual data layer.
Fatal problemsQueries of this category provide information about problems that render a part of a database unusable.
Missing dataQueries of this category provide information about missing data (NULLs) in a database.
Triggers and rulesQueries of this category provide information about triggers and rules in a database.
User-defined routinesQueries of this category provide information about the user-defined routines

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