SQLite Combine Value of Two Columns

问题

I am trying get data from database based on some logic, here is the query

String sql = "SELECT pr.number, pr.u_id from pro_cap pr " +
"LEFT OUTER JOIN pending p " +
"WHERE p.mobile_id = pr.u_id+pr.infant_no ";

Where, value of mobile_id in pending table is 4711

And value of u_id is 471 and value of number is 1 in pro_cap table

I suppose to get data from database where 4711 = 4711, but unable to get...

回答1:

For concatenating two or more columns use || operator.

Change your query as below :

String sql = "SELECT pr.number, pr.u_id from pro_cap pr " +
"LEFT OUTER JOIN pending p " +
"WHERE p.mobile_id = pr.u_id || pr.infant_no ";

来源：https://stackoverflow.com/questions/41015994/sqlite-combine-value-of-two-columns