I want to be able to extract text from jsonb array in a new column as text.
This is my SQL table.
Id.
ErrorCode.
101
["exit code: 1"]
102
["exit code: 3"]
103
["OOMKILLED"]
This is my column definition '[]'::jsonb
I needed help understanding which select command I could use in that case. I used the query above but with no success.
Select reasons -> ' ' as TTT from my_table
I want to get these results after a select command., so I can do SQL filters like
where error = 'exit code: 1' or where error = 'OOMKILLED'
Id.
Error
101
exit code: 1
102
exit code: 3
103
OOMKILLED
Use ->> to extract the first array element as text:
Select id, reasons ->> 0 as reason
from my_table
where reasons ->> 0 in ('exit code: 1','OOMKILLED');
If you don't want to repeat the expression use a derived table:
select *
from (
select id, reasons ->> 0 as reason
from my_table
)
where reason in ('exit code: 1','OOMKILLED');
try this :
SELECT Id, jsonb_array_elements_text(ErrorCode :: jsonb) AS Error
FROM my_table
For more info about json functions see the manual
When you need check is JSONB array contains some value, just use ? operator:
select * from t where err ? 'OOMKILLED';
https://sqlize.online/s/eW
Related
Let's suppose I have a table my_table with a field named data, of type jsonb, which thus contains a json data structure.
let's suppose that if I run
select id, data from my_table where id=10;
I get
id | data
------------------------------------------------------------------------------------------
10 | {
|"key_1": "value_1" ,
|"key_2": ["value_list_element_1", "value_list_element_2", "value_list_element_3" ],
|"key_3": {
| "key_3_1": "value_3_1",
| "key_3_2": {"key_3_2_1": "value_3_2_1", "key_3_2_2": "value_3_2_2"},
| "key_3_3": "value_3_3"
| }
| }
so in pretty formatting, the content of column data is
{
"key_1": "value_1",
"key_2": [
"value_list_element_1",
"value_list_element_2",
"value_list_element_3"
],
"key_3": {
"key_3_1": "value_3_1",
"key_3_2": {
"key_3_2_1": "value_3_2_1",
"key_3_2_2": "value_3_2_2"
},
"key_3_3": "value_3_3"
}
}
I know that If I want to get directly in a column the value of a key (of "level 1") of the json, I can do it with the ->> operator.
For example, if I want to get the value of key_2, what I do is
select id, data->>'key_2' alias_for_key_2 from my_table where id=10;
which returns
id | alias_for_key_2
------------------------------------------------------------------------------------------
10 |["value_list_element_1", "value_list_element_2", "value_list_element_3" ]
Now let's suppose I want to get the value of key_3_2_1, that is value_3_2_1.
How can I do it?
I have tryed with
select id, data->>'key_3'->>'key_3_2'->>'key_3_2_1' alias_for_key_3_2_1 from my_table where id=10;
but I get
select id, data->>'key_3'->>'key_3_2'->>'key_3_2_1' alias_for_key_3_2_1 from my_table where id=10;
^
HINT: No operators found with name and argument types provided. Types may need to be converted explicitly.
what am I doing wrong?
The problem in the query
select id, data->>'key_3'->>'key_3_2'->>'key_3_2_1' alias_for_key_3_2_1 --this is wrong!
from my_table
where id=10;
was that by using the ->> operand I was turning a json to a string, so that with the next ->> operand I was trying to get a json key object key_3_2 out of a string object, which makes no sense.
Thus one has to use the -> operand, which does not convert json into string, until one gets to the "final" key.
so the query I was looking for was
select id, data->'key_3'->'key_3_2'->>'key_3_2_1' alias_for_key_3_2_1 --final ->> : this gets the value of 'key_3_2_1' as string
from my_table
where id=10;
or either
select id, data->'key_3'->'key_3_2'->'key_3_2_1' alias_for_key_3_2_1 --final -> : this gets the value of 'key_3_2_1' as json / jsonb
from my_table
where id=10;
More info on JSON Functions and Operators can be find here
Table has column, named "config" with following content:
{
"A":{
"B":[
{"name":"someName","version":"someVersion"},
{"name":"someName","version":"someVersion"}
]
}
}
The task is to select all name and version values. The output is expected selection with 2 columns: name and value.
I successfully select the content of B:
select config::json -> 'A' -> 'B' as B
from my_table;
But when I'm trying to do something like:
select config::json -> 'A' -> 'B' ->> 'name' as name,
config::json -> 'A' -> 'B' ->> 'version' as version
from my_table;
I receive selection with empty-value columns
If the array size is fixed, you just need to tell which element of the array you want to retrieve,e.g.:
SELECT config->'A'->'B'->0->>'name' AS name,
config->'A'->'B'->0->>'version' AS version
FROM my_table;
But as your array contains multiple elements, use the function jsonb_array_elements in a subquery or CTE and in the outer query parse the each element individually, e.g:
SELECT rec->>'name', rec->>'version'
FROM (SELECT jsonb_array_elements(config->'A'->'B')
FROM my_table) j (rec);
Demo: db<>fiddle
First you should use the jsonb data type instead of json, see the documentation :
In general, most applications should prefer to store JSON data as
jsonb, unless there are quite specialized needs, such as legacy
assumptions about ordering of object keys.
Using jsonb, you can do the following :
SELECT DISTINCT ON (c) c->'name' AS name, c->'version' AS version
FROM my_table
CROSS JOIN LATERAL jsonb_path_query(config :: jsonb, '$.** ? (exists(#.name))') AS c
dbfiddle
select e.value ->> 'name', e.value ->> 'version'
from
my_table cross join json_array_elements(config::json -> 'A' -> 'B') e
I have a table mytable and a JSONB column employees that contains data like this:
[ {
"name":"Raj",
"email":"raj#gmail.com",
"age":32
},
{
"name":"Mohan",
"email":"Mohan#yahoo.com",
"age":21
}
]
I would like to extract only the names and save them in a list format, so the resulting cell would look like this:
['Raj','Mohan']
I have tried
select l1.obj ->> 'name' names
from mytable t
cross join jsonb_array_elements(t.employees) as l1(obj)
but this only returns the name of the first array element.
How do I get the name of all array elements?
Thanks!
PostgreSQL 11.8
In Postgres 12, you can use jsonb_path_query_array():
select jsonb_path_query_array(employees, '$[*].name') as names
from mytable
In earlier versions you need to unnest then aggregate back:
select (select jsonb_agg(e -> 'name')
from jsonb_array_elements(employees) as t(e)) as names
from mytable
I am using Azure CosmosDB to store documents (JSON).
I am trying to query all documents that contain the field "abc", and not return the documents that do not have the field "abc". For example, return the first object below and not the second
{
"abc": "123"
}
{
"jkl": "098"
}
I am trying to use the following code:
client.queryDocuments(
collectionUrl,
`SELECT r.id, r.authToken.instagram,r.userName FROM root r WHERE r.abc`
)
I assumed the above would check if abc exists similar to if (r.abc) {}
I have tried using WHERE r.abc IS NOT NULL
Thanks in advance
If you want to know if a field exists you should use the IS_DEFINED("FieldName")
If you want to know if the field's value has a value the
FieldName != null or
FieldName <> null (apparently)
I use variations of this in production:
SELECT c.FieldName
FROM c
WHERE IS_DEFINED(c.FieldName)
All you need to do is change your query to
SELECT r.id, r.authToken.instagram,r.userName FROM root r WHERE r.abc != null
or
SELECT r.id, r.authToken.instagram,r.userName FROM root r WHERE r.abc <> null
Both operators work (tested on the Data Explorer)
Add the NOT operator in the SQL query to negate.
SELECT r.id, r.authToken.instagram,r.userName
FROM root r
WHERE NOT IS_DEFINED(r.abc)
to include all entries where the FieldName abc doesn't exist.
Test data
DROP TABLE t;
CREATE TABLE t(_id serial PRIMARY KEY, data jsonb);
INSERT INTO t(data) VALUES
('{"a":1,"b":2, "c":3}')
, ('{"a":11,"b":12, "c":13}')
, ('{"a":21,"b":22, "c":23}')
Problem statement: I want to receive an arbitrary JSONB parameter which acts as a filter on column t.data, such as
{ "b":{ "from":0, "to":20 }, "c":13 }
and use this to select matching rows from my test table t.
In this example, I want rows where b is between 0 and 20 and c = 13.
No error is required if the filter specifies a "column" (or "tag") which does not exist in t.data - it just fails to find a match.
I've used numeric values for simplicity but would like an approach which generalises to text as well.
What I have tried so far. I looked at the containment approach, which works for equality conditions, but am stumped on a generic way of handling range conditions:
select * from t
where t.data#> '{"c":13}'::jsonb;
Background: This problem arose when building a generic table-preview page on a website (for Admin users).
The page displays a filter based on various columns in whichever table is selected for preview.
The filter is then passed to a function in Postgres DB which applies this dynamic filter condition to the table.
It returns a jsonb array of the rows matching the filter specified by the user.
This jsonb array is then used to populate the Preview resultset.
The columns which make up the filter may change.
My Postgres version is 9.6 - thanks.
if you want to parse { "b":{ "from":0, "to":20 }, "c":13 } you need a parser. It is out of scope of json functions, but you can write "generic" query using AND and OR to filter by such json, eg:
https://www.db-fiddle.com/f/jAPBQggG3p7CxqbKLMbPKw/0
with filt(f) as (values('{ "b":{ "from":0, "to":20 }, "c":13 }'::json))
select *
from t
join filt on
(f->'b'->>'from')::int < (data->>'b')::int
and
(f->'b'->>'to')::int > (data->>'b')::int
and
(data->>'c')::int = (f->>'c')::int
;
Thanks for the comments/suggestions.
I will definitely look at GraphQL when I have more time - I'm working under a tight deadline at the moment.
It seems the consensus is that a fully generic solution is not achievable without a parser.
However, I got a workable first draft - it's far from ideal but we can work with it. Any comments/improvements are welcome ...
Test data (expanded to include dates & text fields)
DROP TABLE t;
CREATE TABLE t(_id serial PRIMARY KEY, data jsonb);
INSERT INTO t(data) VALUES
('{"a":1,"b":2, "c":3, "d":"2018-03-10", "e":"2018-03-10", "f":"Blah blah" }')
, ('{"a":11,"b":12, "c":13, "d":"2018-03-14", "e":"2018-03-14", "f":"Howzat!"}')
, ('{"a":21,"b":22, "c":23, "d":"2018-03-14", "e":"2018-03-14", "f":"Blah blah"}')
First draft of code to apply a jsonb filter dynamically, but with restrictions on what syntax is supported.
Also, it just fails silently if the syntax supplied does not match what it expects.
Timestamp handling a bit kludgey, too.
-- Handle timestamp & text types as well as int
-- See is_timestamp(text) function at bottom
with cte as (
select t.data, f.filt, fk.key
from t
, ( values ('{ "a":11, "b":{ "from":0, "to":20 }, "c":13, "d":"2018-03-14", "e":{ "from":"2018-03-11", "to": "2018-03-14" }, "f":"Howzat!" }'::jsonb ) ) as f(filt) -- equiv to cross join
, lateral (select * from jsonb_each(f.filt)) as fk
)
select data, filt --, key, jsonb_typeof(filt->key), jsonb_typeof(filt->key->'from'), is_timestamp((filt->key)::text), is_timestamp((filt->key->'from')::text)
from cte
where
case when (filt->key->>'from') is null then
case jsonb_typeof(filt->key)
when 'number' then (data->>key)::numeric = (filt->>key)::numeric
when 'string' then
case is_timestamp( (filt->key)::text )
when true then (data->>key)::timestamp = (filt->>key)::timestamp
else (data->>key)::text = (filt->>key)::text
end
when 'boolean' then (data->>key)::boolean = (filt->>key)::boolean
else false
end
else
case jsonb_typeof(filt->key->'from')
when 'number' then (data->>key)::numeric between (filt->key->>'from')::numeric and (filt->key->>'to')::numeric
when 'string' then
case is_timestamp( (filt->key->'from')::text )
when true then (data->>key)::timestamp between (filt->key->>'from')::timestamp and (filt->key->>'to')::timestamp
else (data->>key)::text between (filt->key->>'from')::text and (filt->key->>'to')::text
end
when 'boolean' then false
else false
end
end
group by data, filt
having count(*) = ( select count(distinct key) from cte ) -- must match on all filter elements
;
create or replace function is_timestamp(s text) returns boolean as $$
begin
perform s::timestamp;
return true;
exception when others then
return false;
end;
$$ strict language plpgsql immutable;