Select datatype of the field in postgres

Question

How do I get datatype of specific field from table in postgres ? For example I have the following table, student_details ( stu_id integer, stu_name varcha

Answer 1

run psql -E and then \d student_details

Answer 2

You can get data types from the information_schema (8.4 docs referenced here, but this is not a new feature):

=# select column_name, data_type from information_schema.columns
-# where table_name = 'config';
    column_name     | data_type 
--------------------+-----------
 id                 | integer
 default_printer_id | integer
 master_host_enable | boolean
(3 rows)

Answer 3

You can use the pg_typeof() function, which also works well for arbitrary values.

SELECT pg_typeof("stu_id"), pg_typeof(100) from student_details limit 1;

Answer 4

If you like 'Mike Sherrill' solution but don't want to use psql, I used this query to get the missing information:

select column_name,
case 
    when domain_name is not null then domain_name
    when data_type='character varying' THEN 'varchar('||character_maximum_length||')'
    when data_type='numeric' THEN 'numeric('||numeric_precision||','||numeric_scale||')'
    else data_type
end as myType
from information_schema.columns
where table_name='test'

with result:

column_name |     myType
-------------+-------------------
 test_id     | test_domain
 test_vc     | varchar(15)
 test_n      | numeric(15,3)
 big_n       | bigint
 ip_addr     | inet

Answer 5

Try this request :

SELECT column_name, data_type FROM information_schema.columns WHERE 
table_name = 'YOUR_TABLE' AND column_name = 'YOUR_FIELD';

Answer 6

Pulling data type from information_schema is possible, but not convenient (requires joining several columns with a case statement). Alternatively one can use format_type built-in function to do that, but it works on internal type identifiers that are visible in pg_attribute but not in information_schema. Example

SELECT a.attname as column_name, format_type(a.atttypid, a.atttypmod) AS data_type
FROM pg_attribute a JOIN pg_class b ON a.attrelid = b.relfilenode
WHERE a.attnum > 0 -- hide internal columns
AND NOT a.attisdropped -- hide deleted columns
AND b.oid = 'my_table'::regclass::oid; -- example way to find pg_class entry for a table

Based on https://gis.stackexchange.com/a/97834.