postgresql-9.3

On PostgreSQL 9.3.4, I have a JSON type column called "person" and the data stored in it is in the format {dogs: [{breed: <>, name: <>}, {breed: <>, name: <>}]} . I want to retrieve the breed of dog at index 0. Here are the two queries I ran: Doesn't work db=> select person->'dogs'->>0->'breed' from people where id = 77; ERROR: operator does not exist: text -> unknown LINE 1: select person->'dogs'->>0->'bree... ^ HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts. Works select (person->'dogs'->>0)::json->'breed' from es_config_app

I have a table to store information about my rabbits. It looks like this: create table rabbits (rabbit_id bigserial primary key, info json not null); insert into rabbits (info) values ('{"name":"Henry", "food":["lettuce","carrots"]}'), ('{"name":"Herald","food":["carrots","zucchini"]}'), ('{"name":"Helen", "food":["lettuce","cheese"]}'); How should I find the rabbits who like carrots? I came up with this: select info->>'name' from rabbits where exists ( select 1 from json_array_elements(info->'food') as food where food::text = '"carrots"' ); I don't like that query. It's a mess. As a full-time

Is there an easy way to list all tables from PostgreSQL database and order them by size? Pseudo-code SELECT * FROM tables ORDER by tables.size I am using PostgreSQL 9.3.2 . select table_name, pg_relation_size(quote_ident(table_name)) from information_schema.tables where table_schema = 'public' order by 2 This shows you the size of all tables in the schema public if you have multiple schemas, you might want to use: select table_schema, table_name, pg_relation_size('"'||table_schema||'"."'||table_name||'"') from information_schema.tables order by 3 SQLFiddle example: http://sqlfiddle.com/#!15

To find the number of days between two dates we can use something like this: SELECT date_part('day',age('2017-01-31','2017-01-01')) as total_days; In the above query we got 30 as output instead of 31. Why is that? And I also want to find the number of days except Sundays. Expected output for the interval ('2017-01-01', '2017-01-31') : Total Days = 31 Total Days except Sundays = 26 You need to define "between two dates" more closely. Lower and upper bound included or excluded? A common definition would be to include the lower and exclude the upper bound of an interval. Plus, define the result

I have a table of rows with the following structure name TEXT, favorite_colors TEXT[], group_name INTEGER where each row has a list of everyone's favorite colors and the group that person belongs to. How can I GROUP BY group_name and return a list of the most common colors in each group? Could you do a combination of int[] && int[] to set for overlap, int[] & int[] to get the intersection and then something else to count and rank? Quick and dirty: SELECT group_name, color, count(*) AS ct FROM ( SELECT group_name, unnest(favorite_colors) AS color FROM tbl ) sub GROUP BY 1,2 ORDER BY 1,3 DESC;

I'm using SQL Alchemy and have some schema's that are account specific. The name of the schema is derived using the account ID, so I don't have the name of the schema until I hit my application service or repository layer. I'm wondering if it's possible to run a query against an entity that has it's schema dynamically set at runtime? I know I need to set the __table_args__['schema'] and have tried doing that using the type() built-in, but I always get the following error: could not assemble any primary key columns for mapped table I'm ready to give up and just write straight sql, but I really