Postgresql informationschema DDL samples

@DB Main.sql

-- list all functions in schema
SELECT  proname, prosrc
FROM    pg_catalog.pg_namespace n
JOIN    pg_catalog.pg_proc p
ON      pronamespace = n.oid
WHERE   nspname = 'public';

-- list all tables in schema
SELECT * FROM information_schema.tables 
WHERE table_schema = 'public' 
order by table_name ;

-- list all tables with descriptions in schema
SELECT t.table_name, pg_catalog.obj_description(pgc.oid, 'pg_class')
FROM information_schema.tables t
INNER JOIN pg_catalog.pg_class pgc
ON t.table_name = pgc.relname 
WHERE t.table_type='BASE TABLE'
AND t.table_schema='public' order by table_name ;

SELECT pgc.*, obj_description(oid)
FROM pg_class pgc;
--WHERE relkind = 'r';

-- list all tables with record count in schema
SELECT
  pgClass.relname as tableName,
  pgClass.reltuples as rowCount
FROM
  pg_class pgClass
INNER JOIN
  pg_namespace pgNamespace ON (pgNamespace.oid = pgClass.relnamespace)
WHERE
  pgNamespace.nspname NOT IN ('pg_catalog', 'information_schema') AND
  pgClass.relkind='r' and pgNamespace.nspname='public' 
 order by pgclass.relname;

-- list all tables with no record in schema
SELECT
  pgClass.relname as tableName, 
  pg_catalog.obj_description(pgClass.oid, 'pg_class')
--  ,pgClass.reltuples as rowCount
FROM
  pg_class pgClass
INNER JOIN
  pg_namespace pgNamespace ON (pgNamespace.oid = pgClass.relnamespace)
WHERE
  pgNamespace.nspname NOT IN ('pg_catalog', 'information_schema') AND
  pgClass.relkind='r' and pgNamespace.nspname='public' and pgClass.reltuples=-1
 order by pgclass.relname;

-- list all columns in tables in schema
SELECT *
  FROM information_schema.columns
 WHERE table_schema = 'public'
   AND table_name   = 'test'
     ;

-- list all columns typed with float8 in schema
SELECT *
  FROM information_schema.columns
 WHERE table_schema = 'public'
   AND table_name   = 'test' and udt_name ='float8'
     ;
    
-- list all columns typed with text in schema
SELECT *
  FROM information_schema.columns
 WHERE table_schema = 'public'
    and udt_name ='text'
     ;
    
-- find varchar typed columns with no length in schema
SELECT *
  FROM information_schema.columns
 WHERE table_schema = 'public'
    and udt_name ='varchar' and character_maximum_length is null
     order by table_name , column_name ;

-- list all columns typed with int4 in schema
SELECT *
  FROM information_schema.columns
 WHERE table_schema = 'public' and
    udt_name ='int4'
 order by table_name , column_name;
    
-- list all columns typed with int8 in schema
SELECT *
  FROM information_schema.columns
 WHERE 
 	table_schema = 'public' and
    udt_name ='int8' and
    column_name not in ('id','created_by','updated_by','concurrency_data','national_identifier') and 
    column_name not like '%_id'
 order by table_name , column_name;

-- list all columns typed with float8 in schema
SELECT *
  FROM information_schema.columns
 WHERE table_schema = 'public' and
    udt_name ='float8'
 order by table_name , column_name;
    
-- finding ConcurrencyStamp columns in schema.
SELECT *
  FROM information_schema.columns
 WHERE 
 	table_schema = 'public' and
    column_name ='ConcurrencyStamp'
 order by table_name , column_name;

-- list all column information in schema
select col_description((table_schema||'.'||table_name)::regclass::oid, ordinal_position) as column_comment
, * from information_schema.columns 
WHERE table_schema = 'public' ;
--and table_name = 'table_name';

-- Checking ConcurrencyStamp column comment 
select table_schema , table_name , column_name , column_comment from (select col_description((table_schema||'."'||table_name||'"')::regclass::oid, ordinal_position) as column_comment
, * from information_schema.columns 
WHERE table_schema = 'public') as cd where cd.column_name ='ConcurrencyStamp' and cd.column_comment<>'Tutarlılık Verisi';
--and table_name = 'table_name';

-- inspecting incorrect column names 
select table_schema , table_name , column_name , column_comment from (select col_description((table_schema||'.'||table_name)::regclass::oid, ordinal_position) as column_comment
, * from information_schema.columns 
) as cd where cd.column_name like '% %';
--and table_name = 'table_name';

--select max(scale(cast(x.numeric_colun as numeric))) from the_table x;
--select length(cast(max(abs(trunc(cast(x.numeric_colun as numeric)))) as text)) from the_table x;

-- find tables in schema
SELECT t.table_schema,t.table_name FROM information_schema.TABLES t WHERE t.table_schema='applicationmanagement' ;

-- find foreign keys
SELECT * FROM (SELECT
    pc.conname as constraint_name, 
    conrelid as child_table_id,   
    pclsc.relname as child_table,
    pc.conkey as child_column_id,
    pac.attname as child_column,
    confrelid as parent_table_id,
    pclsp.relname as parent_table,
    pc.confkey as parent_column_id,
    pap.attname as parent_column,   
    nspname as schema_name
FROM 
    (
    SELECT
         connamespace,conname, unnest(conkey) as "conkey", unnest(confkey)
          as "confkey" , conrelid, confrelid, contype
     FROM
        pg_constraint
    ) pc
    JOIN pg_namespace pn ON pc.connamespace = pn.oid
    -- and pn.nspname = 'panmydesk4400'
    JOIN pg_class pclsc ON pc.conrelid = pclsc.oid
    JOIN pg_class pclsp ON pc.confrelid = pclsp.oid
    JOIN pg_attribute pac ON pc.conkey = pac.attnum and pac.attrelid =pclsc.oid
    JOIN pg_attribute pap ON pc.confkey = pap.attnum and pap.attrelid = pclsp.oid
ORDER BY pclsc.relname) t
WHERE t.constraint_name='fk_compnay_taxofficeam';

-- find constraints in schema
select kcu.table_schema,
       kcu.table_name,
       tco.constraint_name,
       kcu.ordinal_position as position,
       kcu.column_name as key_column,
       tco.constraint_type
from information_schema.table_constraints tco
join information_schema.key_column_usage kcu 
     on kcu.constraint_name = tco.constraint_name
     and kcu.constraint_schema = tco.constraint_schema
     and kcu.constraint_name = tco.constraint_name
--where tco.constraint_type = 'PRIMARY KEY'
order by kcu.table_schema,
         kcu.table_name,
         position;