Postgres | How to extract a value from JSON array that contains multiple JSON objects-CodePudding

I have a table that holds a column called additional_info. this column contains a JSON object that looks like that:

    {
        "dbSources": [{
            "destIp": "10.10.10.29",
            "serviceType": "PostgreSql",
            "srcIp": "10.10.10.68",
            "database": "xe",
            "clusterMember": "",
            "dbId": "PostgreSql_10.10.10.29",
            "clusterName": "",
            "host": "",
            "dbUser": "system",
            "osUser": "",
            "userType": "Unknown",
            "srcApp": ""
        },{
            "destIp": "10.10.10.29",
            "serviceType": "PostgreSql",
            "srcIp": "10.10.10.69",
            "database": "xe1",
            "clusterMember": "",
            "dbId": "PostgreSql_10.10.10.29",
            "clusterName": "",
            "host": "",
            "dbUser": "system",
            "osUser": "",
            "userType": "Unknown",
            "srcApp": ""
        }]
    }

I want to extract (to select) the value of "database" where srcIp equals 10.10.10.68. meaning I want to extract the value "xe" from the first JSON object under the JSON array called dbSources.

The only thing that I could do is

    select additional_info::json ->'dbSources' as db from table

but how can I continue from there?

CodePudding user response：

You can do something like that:

with query as (
select j->>'database' as db,j->>'srcIp' as src_ip from json_array_elements('{
        "dbSources": [{
            "destIp": "10.10.10.29",
            "serviceType": "PostgreSql",
            "srcIp": "10.10.10.68",
            "database": "xe",
            "clusterMember": "",
            "dbId": "PostgreSql_10.10.10.29",
            "clusterName": "",
            "host": "",
            "dbUser": "system",
            "osUser": "",
            "userType": "Unknown",
            "srcApp": ""
        },{
            "destIp": "10.10.10.29",
            "serviceType": "PostgreSql",
            "srcIp": "10.10.10.69",
            "database": "xe1",
            "clusterMember": "",
            "dbId": "PostgreSql_10.10.10.29",
            "clusterName": "",
            "host": "",
            "dbUser": "system",
            "osUser": "",
            "userType": "Unknown",
            "srcApp": ""
        }]
    }'::json->'dbSources') as j)
select db from query where src_ip = '10.10.10.68'

CodePudding user response：

Assuming the json is stored as json you can use json functions such as json_array_elements to convert the array into rows, the locate the row containing desired name-value:

select t.id, a.v->>'database'
from t
cross join lateral json_array_elements(t.additional_info->'dbSources') as a(v)
where a.v->>'srcIp' = '10.10.10.68'

CodePudding user response：

You can use a JSON path query:

select jsonb_path_query_first(additional_info, '$.dbSources[*] ? (@.srcIp == "10.10.10.68").database')
from the_table

This assumes the column is of type jsonb (which it should be). If it's not, you need to cast it: additional_info::jsonb