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More importantly: when it comes to querying databases, LINQ is in most cases a significantly more productive querying language than SQL.Compared to SQL, LINQ is simpler, tidier, and higher-level. Sure, there are times when it's still best to use C (as is the case with SQL), but in most situations, working in a modern tidy language and not having to worry about lower-level details is a big win. Since then it's been extended endlessly, but never redesigned. ID in ( SELECT Purchase ID FROM Purchase Item GROUP BY Purchase ID HAVING SUM (Sale Amount) An interesting point is that it's possible to transliterate the above SQL query back into LINQ, yielding a query that's every bit as repetitive - and at least as clumsy.As because LINQ queries are composable, we can add predicates conditionally.For example, we could write a method as follows: SELECT [t0].[ID], [t0].[Name], [t0].[Address ID] FROM [Customer] AS [t0] LEFT OUTER JOIN [Address] AS [t1] ON [t1].[ID] = [t0].[Address ID] WHERE (EXISTS( SELECT NULL AS [EMPTY] FROM [Purchase] AS [t2] WHERE ([t2].[Price] Because our method returns an IQueryable, the query is not actually translated to SQL and run until enumerated.In the case of LINQ to SQL or Entity Framework, the translation engine will convert the query (that we composed in two steps) into a single SQL statement optimized for the database server to which it's connected. Selecting from more than one table in SQL requires joining - the end result being rows of flat tuples.You might have noticed another more subtle (but important) benefit of the LINQ approach. If you've used SQL for many years, you may have become so accepting of this that it may not occur to you that this is often undesirable: it leads to data duplication and makes result sets awkward to work with on the client.This has made the language messy—rather like VB6 or Visual Fox Pro. You'll often see (typically non-working versions of) such queries posted on forums - this happens as a result of thinking in SQL, rather than thinking in LINQ.
This is of real benefit when refactoring: the compiler will tell you if you haven't completely done your job.This give the caller a chance to add further predicates, pagination, custom projections, and so on.In the preceding queries, if we had declared the state variable as an integer rather than a string, the query would fail at compile-time rather than run-time.In LINQ, the query is effortless: SELECT p.* FROM Purchase p LEFT OUTER JOIN Customer c INNER JOIN Address a ON c. In this case, the query, when translated to SQL, would be an outer join: LINQ doesn't exclude rows just because a subcollection returns zero elements.If we wanted something that translated to an inner join, we could do this: LINQ also supports flat outer joins, adhoc joins, subqueries, and numerous other kinds of queries through a rich set of operators.