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When to use array to JSON in PostgreSQL?
I am using array_to_json in combination with array_agg to format certain results in PostgreSQL as JSON. This works fine for queries when I want to return the default value of a query (all columns, unmodified). But I’m stumped how I could use array_agg to create a JSON object for a query where I want to modify some of the output.
How to convert row to array in PostgreSQL?
You can optionally include a row_to_json call in the query: This converts each row to a JSON object, aggregates the JSON objects as an array, and then converts the array to a JSON array. I wasn’t able to discern any significant performance difference between the two.
What is the name of the column in PostgreSQL?
I’m using PostgreSQL. Column name is “sections” and column type is json [] in below example.
How to query array of objects in JSONB field?
Some example rows: I have a list of values for id and want to select any row that contains an object with any of the values from that list, within the array in the jsonb field. Is that possible? Is there a GIN index I can make that will speed this up? 1.
You will want to use array_to_json (array_agg (…)) when you have a 1:many relationship, btw. The above query should ideally be able to be written as: but PostgreSQL’s ROW constructor doesn’t accept AS column aliases. Sadly. Thankfully, they optimize out the same. Compare the plans:
How to update all values nested in JSON array of?
Not trivial in Postgres 10 (would require a tailored expression index). Much simpler and more efficient in Postgres 12 with the SQL/JSON path language: ‘Look at the key “updatedAt” (in all array elements) at the top level and check whether any of them is not equal to “1571150000”; return true if (and only if) such a key is found.’
Why is the type casting necessary in PostgreSQL?
Here are the two queries I ran: 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. Why is the type casting necessary?
How to create JSON object with columns A, B, C?
Anyway, in general, the principle is that where you want to create a json object with columns a, b, c, and you wish you could just write the illegal syntax: