![]() It would be more efficient to store the names in a proper relational table with a one-to-many relationship to the base table ( test_tablica1 in your example) However, your model really looks like a mis-use of JSON in the database. The WHERE clause prevents updating rows that don't need updating The CASE expression will then check each element an if it contains the firstname Maria, the lastname will be replaced (appending a JSONB value to a JSONB value, replaces the existing keys) Jsonb_agg() aggregates the elements that are returned by jsonb_array_elements() back into an array. As podaci contains an array, you need to include the array position, e.g. The second parameter for that function requires a "target path". I don't think this can be done using jsonb_set(). If you have any suggestions on how this sort of thing should be done, I'd be more than happy to get some constructive feedback. I'd be grateful if someone could clarify what I'm doing wrong. I used dbfiddle to test out if what I am doing would work before putting anything into the real database as to not make any unnecessary mistakes. In this case I wanted to update a single element of an array by swapping out one of the 'lastName' values for another using the UPDATE command (the syntax I'm using is probably wrong but that's the most I could work out from what I've read in the official documentation). I want to change a single element of a nested array using the UPDATE, DELETE or INSERT commands. I already asked this question on stackoverflow but I didn't get a conclusive answer so I thought it might be a good idea to ask the same question here since this site is focused solely on databases and their ins and outs. The latter is an embedded JSON.First of all I'd like to say that I don't have much experience but I started learning dbs after having a couple of subjects related to dbs at my university (so please keep that in mind while you're reading this). The sample program below retrieves a list of ‘customer_name’ and then a list of ‘description’ of ‘items’ of the sale. PreparedStatement ps = conn.prepareStatement(sql) įor (int i=0 i’ operator to retrieve values of the various keys in a JSON object. String sql = "INSERT INTO sales VALUES (?, ?::JSON)" The simple Java program below inserts 4 records into the table we just created. The JSON data type checks for a valid JSON format, so insert statements should be mindful of that. We create a table ‘sales’ below (which we will use in subsequent examples) containing 2 columns, ‘id’ and ‘sale’, with the latter being a JSON: json_sample=# CREATE TABLE sales (id INT, sale JSON) Re-parsing is not needed, making data processing significantly fasterĪll white space and line feeds in the input are preserved as-isĮxtra white space and line feeds are strippedĭuplicate keys are retained, processing functions only consider the last valueĭuplicate keys are purged at input, only the last value is storedĪ JSON column is created just like any other data type. Processing functions must re-parse the data on each execution Input is slightly slower, as there is an overhead related to binary conversion Input is fast, as no conversion are required Major differences between JSON & JSONB are highlighted in the table below: JSONB was introduced as a native data type in v9.4 of PostgreSQL and it stores JSON objects in binary format. String manipulation and parsing are very expensive operations in a database, so although you could have potentially stored JSON objects in strings in PostgreSQL before, introduction of the native data type has taken away overheads and made throughput a lot faster for JSON manipulation. Subsequent releases introduced JSONB (binary formatted JSON objects) and many data manipulation functions for JSONs, making it a very powerful tool for NoSQL operations. Starting v9.2, PostgreSQL is providing native data type support for JSON objects. For links to other blogs in this series, please scroll to the end of this post. This is part of a series of blogs on Java & PostgreSQL. PostgreSQL 9 Cookbook – Chinese Edition. ![]()
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