CODEWITHSUNDEEP
pythonsqlalchemy
user14114923
user14114923

Reputation:

How to get a list value of `<class 'flask_sqlalchemy.BaseQuery'>`?

I use the below code of flask

test_flag = db.session.query(TestTable.flag).distinct()

It's SQL of [SQL: SELECT DISTINCT test_table.flag AS test_table_flag FROM test_table

flag
1
2
3

How to get a list value of db.session.query(TestTable.flag).distinct()?

I need the output like this [1,2,3], what I want to do is to ensure whether 2 is in [1,2,3]

Upvotes: 0

Views: 728

Answers (2)

snakecharmerb
snakecharmerb

Reputation: 55799

You can check for the value on the database side, without having to retrieve all the distinct values. This may be more efficient if you don't need all the values at the Python level, or if there are many rows in the table.

# Assuming there are rows containing 1, 2 and 3.

flags = db.session.query(True).filter(db.exists().where(TestTable.flag == 2)).scalar()

flags = db.session.query(True).filter(db.exists().where(TestTable.flag == 4)).scalar()

The first query will return True, the second will return None.

Similarly, you could query for the count of rows with the required value to see if any exist, but the exists construct is more efficient because it will stop searching after finding the first value that matches the filter.

Upvotes: 0

Fareed Khan
Fareed Khan

Reputation: 2923

You can use this to generate list of your flags

flag_list = [each.flag for each in db.session.query(TestTable.flag).distinct()]

Then you can use the below command to ensure whether 2 exist in flag_list or not. If it does exist then it will return True otherwise False

2 in flag_list

Upvotes: 0

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