Effective way in PRESTO to Result output with Boolean values

问题

Im trying to create a output of boolen values on back of some conditions.

OutPut:

EX: I have 3 rules/conditions from different tables which are not related to each other.

Rule 1:

Select USER_NAME, ID from session_user where age > 25

Rule 2:

Select USER_NAME, ID from current_user where plan = 'gold'

Rule 3:

Select USER_NAME, ID from customer where group_name='managers'

My OutPut Should be:

USER_NAME   |  ID | Rule 1 | Rule 2 | Rule 3

user1          1     true    false    true

user2          2     false   true     true

user3          3     true    true     true

If user1 is passing rule one the value should be true for him in the output, if he passed rule 2 then true else false.

Solution:

SELECT  dp.USER_NAME,
        dp.ID, 
        CASE 
            WHEN dp.sex='F' THEN 'True' 
            ELSE 'False' 
        END AS Rule_1,
        CASE 
            WHEN dp.sex='M' THEN 'True' 
            ELSE 'False' 
        END AS Rule_2,
        CASE 
            WHEN dp.sex not in ('M','F') THEN 'True' 
            ELSE 'False' 
        END AS Rule_3
FROM    user_details dp where dp.Organisation='007';

Question:

Is the above select statement is effective way in PRESTO.?
If not what are the other options.
Im new to PRESTO so its difficult to use join in select, How do i form similar output when i join multiple tables? any doc links will be helpful to understand further.
With CASE I cant able to use COUNT how can i add a rule if i want to see COUNT is greater than 2. (Count(*) > 0) = True else False.
Can we use SubQuery in CASE? Will it affect performance?

回答1:

PrestoDB supports boolean values, so no CASE expression is necessary:

SELECT dp.USER_NAME, dp.ID, 
       (dp.sex = 'F') AS Rule_1,
       (dp.sex = 'M') AS Rule_2,
       (dp.sex not in ('M','F')) AS Rule_3
FROM user_details dp 
WHERE dp.Organisation = '007';

I don't see what the rest of your questions have to do with your query. However, StackOverflow questions are limited to a single question. So feel free to ask another question . . . but PrestoDB (like all databases) supports subqueries in CASE expressions.

来源：https://stackoverflow.com/questions/62873767/effective-way-in-presto-to-result-output-with-boolean-values

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sql

database

presto