在PostgreSQL中将json字段值更新为小写

Question

I have a table which includes a json field. One of the key have mixed case values and I want to convert them to lower case. I have tried a few methods to do that, but nothing works and raising explicit cast issues.

UPDATE table SET data = LOWER( CAST (data AS json)) WHERE id=123;

Above query raised the following error.

No function matches the given name and argument types. You might need to add explicit type casts.

• I have also tried to update particular key but that also raised the same kind of error.
• I am not sure if PostgreSQL allowed such kind of operation on json data

Answer 1

lower() is for type text . So first cast your json data into text. After lower() execution you can cast it back into type json :

UPDATE a SET data = LOWER(data::text)::json;

demo:db<>fiddle