postgres-syntax-cheatsheet
Some common PostgreSQL syntax examples I keep forgetting
Containment
select * from SOME_TABLE where SOME_ARRAY_COLUMN @> '{Red, Blue}';Returning nested data as JSON
select
id, created_at, name,
(select to_json(u) from (select id from users where users.id = user_id) as u) as user,
(select to_json(d) from (select id from dbs where dbs.id = db_id) as d) as db
from snippets
where user_id = $1 id | created_at | name | user | db
----+-------------------------------+------------------------------+----------+----------
5 | 2015-05-22 17:42:40.368898-05 | dsadasda | {"id":1} | {"id":1}
7 | 2015-05-22 17:45:08.840262-05 | dsadasda | {"id":1} | {"id":1}
8 | 2015-05-22 17:47:23.528823-05 | poop | {"id":1} | {"id":1}
This is much better than returning foreign keys like user_id, db_id
[
{
id: 5,
created_at: '2015-05-22 17:42:40.368898-05',
name: 'dsadasda',
user_id: 1,
db_id: 1
}
]If you wanted more user or db info, you'd have to add more top level keys like user_name, database_name. This is shitty.
[
{
id: 5,
created_at: '2015-05-22 17:42:40.368898-05',
name: 'dsadasda',
user_id: 1,
user_name: 'Preston',
db_id: 1,
db_name: 'foo'
}
]Instead, using the above nested json querying we can provide better hierarchy:
[
{
id: 5,
created_at: '2015-05-22 17:42:40.368898-05',
name: 'dsadasda',
user: { id: 1, name: 'Preston' }
db: { id: 1, name: 'foo' }
}
]Querying JSON
get key as text
select person->>'dogs';get nested keys, note that -> returns value as json
select person->'dogs'->0->'breed' from people where id = 77;Output table as html
discovered in http://www.postgresonline.com/downloads/special_feature/postgresql83_psql_cheatsheet.pdf
psql -c "select * from dogs" -H -o dogs.html