SQL,LINQ,Lambda语法对照图（转载）

Love The Way You Lie 2021-11-27 06:46 231阅读 0赞

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语法对照图

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

转载于:https://www.cnblogs.com/CielWater/p/3528718.html