Execute query on multiple sqlite databases in C#

Question

I have more than 400 sqlite databases. I need to query on these databases. Like simple SELECT..... query to get results.

I don't know weather it is possible within single query.

Current logic is.

foreach(FileInfo finf in Files)
{
    // query one database get result 
    Datatable results = execute();
    // merge Datatable with new one.
}

at the end we get all database results in single datatable.

Is anyone having better solution for querying multiple databases?

Thanks in advance.

yes i tried but maximum results are related to attach database. Which is inconvenience to me. It is same as current logic — Pratik
– Pratik, Commented Jan 17, 2014 at 7:18
your solution is not bad, but close unused SqLiteConnection(s) — houssam
– houssam, Commented Jan 17, 2014 at 21:21

Antonio Petricca · Accepted Answer · 2014-01-17 07:28:32Z

1

In order to get a single result set with SQLite you have to join all the databases by the ATTACH command giving to each one a different alias, then build a sql statement which group the data into a single result set by the SELECT ... UNION command.

For example:

 - ATTACH DATABASE 'Database1' As 'DB1';
 - ATTACH DATABASE 'Database2' As 'DB2';

Then :

SELECT * FROM DB1.MyTable

UNION

SELECT * FROM DB2.MyTable

answered Jan 17, 2014 at 7:28

Antonio Petricca

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2 Comments

Pratik Over a year ago

I have more than 400 database. max limit of sqlite attach database is 62. sqlite.org/limits.html

Antonio Petricca Over a year ago

Query by group og 62 queries and merge the results into DataTable object.

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