SQL,LINQ,Lambda语法对照图（转载）

时间：2024-08-06 16:04:14

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

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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