SQL-LINQ-Lambda语法对照实例

如果你熟悉SQL语句,当使用LINQ时,会有似曾相识的感觉.但又略有不同.下面是SQL和LINQ,Lambda语法对照

SQL	LINQ	Lambda
SELECT *FROM HumanResources.Employee	from e in Employees select e	Employees .Select (e => e)
SELECT e.LoginID, e.JobTitle FROM HumanResources.Employee AS e	from e in Employees select new {e.LoginID, e.JobTitle}	Employees.Select (       e => new {             LoginID = e.LoginID,              JobTitle = e.JobTitle          }    )
SELECT e.LoginID AS ID, e.JobTitle AS Title FROM HumanResources.Employee AS e	from e in Employees select new {ID = e.LoginID, Title = e.JobTitle}	Employees.Select (       e => new           {             ID = e.LoginID,              Title = e.JobTitle          }    )
SELECT DISTINCT e.JobTitle FROM HumanResources.Employee AS e	(from e in Employees select e.JobTitle).Distinct()	Employees    .Select (e => e.JobTitle)    .Distinct ()
SELECT e.* FROM HumanResources.Employee AS e WHERE e.LoginID = 'test'	from e in Employees where e.LoginID == "test" select e	Employees    .Where (e => (e.LoginID == "test"))
SELECT e.* FROM HumanResources.Employee AS e WHERE e.LoginID = 'test' AND e.SalariedFlag = 1	from e in Employees where e.LoginID == "test" && e.SalariedFlag select e	Employees    .Where (e => ((e.LoginID == "test") && e.SalariedFlag))
SELECT e.* FROM HumanResources.Employee AS e WHERE e.VacationHours >= 2 AND e.VacationHours <= 10	from e in Employees where e.VacationHours >= 2 && e.VacationHours <= 10 select e	Employees    .Where (e => (((Int32)(e.VacationHours) >= 2) && ((Int32)(e.VacationHours) <= 10)))
SELECT e.* FROM HumanResources.Employee AS e ORDER BY e.NationalIDNumber	from e in Employees orderby e.NationalIDNumber select e	Employees    .OrderBy (e => e.NationalIDNumber)
SELECT e.* FROM HumanResources.Employee AS e ORDER BY e.HireDate DESC, e.NationalIDNumber	from e in Employees orderby e.HireDate descending, e.NationalIDNumber select e	Employees    .OrderByDescending (e => e.HireDate)    .ThenBy (e => e.NationalIDNumber)
SELECT e.* FROM HumanResources.Employee AS e WHERE e.JobTitle LIKE 'Vice%' OR SUBSTRING(e.JobTitle, 0, 3) = 'Pro'	from e in Employees where e.JobTitle.StartsWith("Vice") || e.JobTitle.Substring(0, 3) == "Pro" select e	Employees    .Where (e => (e.JobTitle.StartsWith ("Vice") || (e.JobTitle.Substring (0, 3) == "Pro")))
SELECT SUM(e.VacationHours) FROM HumanResources.Employee AS e		Employees.Sum(e => e.VacationHours);
SELECT COUNT(*) FROM HumanResources.Employee AS e		Employees.Count();
SELECT SUM(e.VacationHours) AS TotalVacations, e.JobTitle FROM HumanResources.Employee AS e GROUP BY e.JobTitle	from e in Employees group e by e.JobTitle into g select new {JobTitle = g.Key, TotalVacations = g.Sum(e => e.VacationHours)}	Employees    .GroupBy (e => e.JobTitle)    .Select (       g => new           {             JobTitle = g.Key,              TotalVacations = g.Sum (e => (Int32)(e.VacationHours))          }    )
SELECT e.JobTitle, SUM(e.VacationHours) AS TotalVacations FROM HumanResources.Employee AS e GROUP BY e.JobTitle HAVING e.COUNT(*) > 2	from e in Employees group e by e.JobTitle into g where g.Count() > 2 select new {JobTitle = g.Key, TotalVacations = g.Sum(e => e.VacationHours)}	Employees    .GroupBy (e => e.JobTitle)    .Where (g => (g.Count () > 2))    .Select (       g =>           new           {             JobTitle = g.Key,              TotalVacations = g.Sum (e => (Int32)(e.VacationHours))          }    )
SELECT * FROM Production.Product AS p, Production.ProductReview AS pr	from p in Products from pr in ProductReviews select new {p, pr}	Products    .SelectMany (       p => ProductReviews,        (p, pr) =>           new           {             p = p,              pr = pr          }    )
SELECT * FROM Production.Product AS p INNER JOIN Production.ProductReview AS pr ON p.ProductID = pr.ProductID	from p in Products join pr in ProductReviews on p.ProductID equals pr.ProductID select new {p, pr}	Products    .Join (       ProductReviews,        p => p.ProductID,        pr => pr.ProductID,        (p, pr) =>           new           {             p = p,              pr = pr          }    )
SELECT * FROM Production.Product AS p INNER JOIN Production.ProductCostHistory AS pch ON p.ProductID = pch.ProductID AND p.SellStartDate = pch.StartDate	from p in Products join pch in ProductCostHistories on new {p.ProductID, StartDate = p.SellStartDate} equals new {pch.ProductID, StartDate = pch.StartDate} select new {p, pch}	Products    .Join (       ProductCostHistories,        p =>           new           {             ProductID = p.ProductID,             StartDate = p.SellStartDate          },        pch =>           new           {             ProductID = pch.ProductID,              StartDate = pch.StartDate          },        (p, pch) =>           new           {             p = p,              pch = pch          }    )
SELECT * FROM Production.Product AS p LEFT OUTER JOIN Production.ProductReview AS pr ON p.ProductID = pr.ProductID	from p in Products join pr in ProductReviews on p.ProductID equals pr.ProductID into prodrev select new {p, prodrev}	Products    .GroupJoin (       ProductReviews,        p => p.ProductID,        pr => pr.ProductID,        (p, prodrev) =>           new           {             p = p,              prodrev = prodrev          }    )
SELECT p.ProductID AS ID FROM Production.Product AS p UNION SELECT pr.ProductReviewID FROM Production.ProductReview AS pr	(from p in Products select new {ID = p.ProductID}).Union( from pr in ProductReviews select new {ID = pr.ProductReviewID})	Products    .Select (       p =>           new           {             ID = p.ProductID          }    )    .Union (       ProductReviews          .Select (             pr =>                 new                 {                   ID = pr.ProductReviewID                }          )    )
SELECT TOP (10) * FROM Production.Product AS p WHERE p.StandardCost < 100	(from p in Products where p.StandardCost < 100 select p).Take(10)	Products    .Where (p => (p.StandardCost < 100))    .Take (10)
SELECT * FROM [Production].[Product] AS p WHERE p.ProductID IN(     SELECT pr.ProductID     FROM [Production].[ProductReview] AS [pr]     WHERE pr.[Rating] = 5     )	from p in Products where (from pr in ProductReviews where pr.Rating == 5 select pr.ProductID).Contains(p.ProductID) select p	Products    .Where (       p =>           ProductReviews             .Where (pr => (pr.Rating == 5))             .Select (pr => pr.ProductID)             .Contains (p.ProductID)    )

直接上实例，学习起来是不是更方便些！参考阅读：http://www.58os.com/BBS/PublicBSS/Article-123.html