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Querying from multiple tables in Android SQLite?

开发者 https://www.devze.com 2023-03-19 14:33 出处:网络
I was wondering if it\'s possible (it should be) to query multiple tables simultaneously (several at once) in SQLite. Basically I have several tables that have the exact same columns, but the data in

I was wondering if it's possible (it should be) to query multiple tables simultaneously (several at once) in SQLite. Basically I have several tables that have the exact same columns, but the data in them is just organized by the table it's in. I need to be able to use SELECT to get data from the tables (I heard UNION could help), which matches a condition, then group the data by the table it's in.

In other words, would something like this be possible?

SELECT * FROM table1,table2,table3,table4,table5,table6 WHERE day=15 GROUP BY {table}

I'd rather not resort to having to query the tables individually as then I would have a bunch of Cursors that I'd have to manually go through and that would be difficult when I only have one SimpleCursorAdapter? Unless a SimpleCursorAdapter can have several Cursors?

Than开发者_Go百科ks.

EDIT: The structure of my tables:

Main Table - contains references to subtables in a column "tbls"
             and meta-information about the data stored in the subtables

    Subtable - contains reference to subsubtables in a column "tbls"
               and meta-information about the data stored in the
               subsubtables

        Subsubtable - contains the actual entries

Basically these tables just make it easier to organize the hierarchical data structure. I suppose instead of having the subsubtables, I could keep the actual entries in the subtable but add a prefix, and have a separate table for the meta-information. It just seems it would be harder to delete/update the structure if I need to remove a level in this data set.


You can create view based on your tables, the query of your view is union of your tables.

create view test as select * from table1 union select * from table2

now you can filter data as you want for more info check union & view

http://www.w3schools.com/sql/sql_union.asp

http://www.w3schools.com/sql/sql_view.asp


In the end, I decided to forgo having many subsubtables, and instead adding another column like Tim and Samuel suggested. It will probably be more efficient as well then chaining SELECTs with UNION.

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