I think answer 4 is correct. There are a few considerations: type of subquery – is it corrrelated, or not. Consider: SELECT * FROM t1 WHERE id IN ( SELECT id FROM t2 ) Here, the subquery is not correlated to the outer query. If the number of values in t2.id is small in comparison … Read more
INSERT INTO Results (People, names ) SELECT d.id, ‘Henry’ FROM Names f JOIN People d ON d.id = f.id Combine the static string Henry with your SELECT query.
A great resource on calculating running totals in SQL Server is this document by Itzik Ben Gan that was submitted to the SQL Server Team as part of his campaign to have the OVER clause extended further from its initial SQL Server 2005 implementation. In it he shows how once you get into tens of … Read more
Based on the information in the article you linked to this should work: update giveaways set winner=”1″ where Id = (select Id from (select max(Id) as id from giveaways) as t)
Above example is not Co-related Sub-Query. It is Derived Table / Inline-View since i.e, a Sub-query within FROM Clause. A Corelated Sub-query should refer its parent(main Query) Table in it. For example See find the Nth max salary by Co-related Sub-query: SELECT Salary FROM Employee E1 WHERE N-1 = (SELECT COUNT(*) FROM Employee E2 WHERE … Read more
And for people who don’t quite get what the documentation is saying, a SUBQUERY is essentially this: SUBQUERY(collection, variableName, predicateFormat) And could (simplistically) be implemented like this: id resultingCollection = …; //a new collection, either a mutable set or array NSMutableDictionary * substitutions = [NSMutableDictionary dictionary]; NSPredicate * p = [NSPredicate predicateWithFormat:predicateFormat]; for (id variable … Read more
Rails now does this by default 🙂 Message.where(user_id: Profile.select(“user_id”).where(gender: ‘m’)) will produce the following SQL SELECT “messages”.* FROM “messages” WHERE “messages”.”user_id” IN (SELECT user_id FROM “profiles” WHERE “profiles”.”gender” = ‘m’) (the version number that “now” refers to is most likely 3.2)
You want: insert into prices (group, id, price) select 7, articleId, 1.50 from article where name like ‘ABC%’; where you just hardcode the constant fields.
SELECT (sub)queries return result sets. So you need to use IN, not = in your WHERE clause. Additionally, as shown in this answer you cannot modify the same table from a subquery within the same query. However, you can either SELECT then DELETE in separate queries, or nest another subquery and alias the inner subquery … Read more
The subquery is being run for each row because it is a correlated query. One can make a correlated query into a non-correlated query by selecting everything from the subquery, like so: SELECT * FROM ( SELECT relevant_field FROM some_table GROUP BY relevant_field HAVING COUNT(*) > 1 ) AS subquery The final query would look … Read more