SQL-LINQ-Lambda语法对照

Posted 2020-11-01 达者均为吾师

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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)
   )

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