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• How to implement filter system in SQL?

  - by sadvaw

  Right now I am planning to add a filter system to my site. Examples: (ID=apple, COLOR=red, TASTE=sweet, ORIGIN=US) (ID=mango, COLOR=yellow, TASTE=sweet, ORIGIN=MEXICO) (ID=banana, COLOR=yellow, TASTE=bitter-sweet, ORIGIN=US) so now I am interested in doing the following: SELECT ID FROM thisTable WHERE COLOR='yellow' AND TASTE='SWEET' But my problem is I am doing this for multiple categories in my site, and the columns are NOT consistent. (like if the table is for handphones, then it will be BRAND, 3G-ENABLED, PRICE, COLOR, WAVELENGTH, etc) how could I design a general schema that allows this? Right now I am planning on doing: table(ID, KEY, VALUE) This allows arbitary number of columns, but for the query, I am using SELECT ID FROM table WHERE (KEY=X1 AND VALUE=V1) AND (KEY=X2 AND VALUE=V2), .. which returns an empty set. Can someone recommend a good solution to this? Note that the number of columns WILL change regularly

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• SQLAlchemy, one to many vs many to one

  - by sadvaw

  Dear Everyone, I have the following data: CREATE TABLE `groups` ( `bookID` INT NOT NULL, `groupID` INT NOT NULL, PRIMARY KEY(`bookID`), KEY( `groupID`) ); and a book table which basically has books( bookID, name, ... ), but WITHOUT groupID. There is no way for me to determine what the groupID is at the time of the insert for books. I want to do this in sqlalchemy. Hence I tried mapping Book to the books joined with groups on book.bookID=groups.bookID. I made the following: tb_groups = Table( 'groups', metadata, Column('bookID', Integer, ForeignKey('books.bookID'), primary_key=True ), Column('groupID', Integer), ) tb_books = Table( 'books', metadata, Column('bookID', Integer, primary_key=True), tb_joinedBookGroup = sql.join( tb_books, tb_groups, \ tb_books.c.bookID == tb_groups.c.bookID) and defined the following mapper: mapper( Group, tb_groups, properties={ 'books': relation(Book, backref='group') }) mapper( Book, tb_joinedBookGroup ) ... However, when I execute this piece of code, I realized that each book object has a field groups, which is a list, and each group object has books field which is a singular assigment. I think my definition here must have been causing sqlalchemy to be confused about the many-to-one vs one-to-many relationship. Can someone help me sort this out? My desired goal is g.books = [b, b, b, .. ] book.group = g, where g is an instance of group, and b is an instance of book

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