#Postgresql case statement how to
#Postgresql case statement code

The SQuAD 2 dataset is an incredibly popular set of question-answer pairs used for training machine-learning models for question-answering. A great test use-case of this is parsing the SQuAD 2 dataset. Real Use-Case With JSONĪnother use-case that looks interesting is the ability to parse dictionary objects differently based on their structure. Which option is preferred may vary, but for me, the match-case implementation looks much cleaner. Now, if we wanted to write this same logic using an if-else statement, we would get this: if isinstance(x, tuple) and len(x) = 2: host, port = x mode = 'http' elif isinstance(x, tuple) and len(x) = 3: host, port, mode = x So rather we might receive a tuple like (,, 'ftp') - in which case we would not want to set mode to “http”. However, in other cases, we may expect that the mode is explicitly defined. However, it takes a month of Sundays and I'm wondering if there is some way of optimizing it. In the example below, homeowner status has three values which break out to three CASE statements but in fact it has 8 potential values. In this case, if the connection mode is not defined within the tuple (e.g., only two values have been provided - the host and port), we assume that the connection mode is “http”. In the case of one field there are 35 possible values which generates 35 different CASE statements. Here we expect to receive connection details in a tuple format and assign the given values to the correct variables.

#Postgresql case statement how to

One of those is this example showing us how to use match-case to check the type and structure of our subject: match x: case host, port: mode = 'http' case host, port, mode: pass

#Postgresql case statement code

We can find some great examples of using the match-case statement to improve code readability in PEP 635. However, by using the match-case statement we remove the repetition of http_code =Which can look much cleaner when testing for many different conditions. Immediately it’s evident that yes, we can build the same logic using a chunk of if-elif-else statements: http_code = '418' if http_code = '418': print('OK') do_something_good() elif http_code = '404': print('Not Found') do_something_bad() elif http_code = '418' print('I'm a teapot') make_coffee() else: print('Code not found') When (destination_host not in (select host from subquery)) THEN 'typeB'īut I don't think this is the way to solve this problem.Flow of logic through the match-case statement.

I tried using case statements such as this one: when (destination_host in (select host from subquery)) THEN 'typeA' Then we begin or execution part where we will place our if statement in which we will check whether age is greater than 18 if.

Then comes the declaration part, where we declare our variable named age and initialize it to 23 integer value. 0 In Oracle Database 21 In PostgreSQL 14 In Microsoft SQL Server 2019 In Teradata 15. I understand that it is hard to provide guidance if you don't have actual data to work with. Explanation: The DO statement specifies that Postgres needs to execute the following statements below it. CASE statements can be used anywhere SELECT within functions, e. Please can you help me understand how to write this.

I want to output a fourth column that is based on a condition check, let's say we call this host_category and if the destination_host value exists in the subquery then I want to add value typeA or else typeB. My select statement looks something like select name, place, destination_host Now I need to check if the destination_host is in the list returned from my subquery, then I want to output TypeA in my select statement or else TypeB. I have a subquery like this with subquery as (select host from table_A where >)Īnd in my main query, I am querying data from another table called table_B, and one of the columns is called destination_host.