我正在使用EntityFramework Core 2.0在Asp.NET Core 2.0项目中工作。
我正在尝试将现有的旧SQL存储过程转换为EntityFramework Core中的Linq，而我在使用这个特定的T-SQL段时遇到了困难;
SET @Target = (SELECT MIN(A.[Serial])
FROM (SELECT [HighSerial] + 1 AS 'Serial'
FROM [Efn]
WHERE [Mid] = @Mid
AND ([HighSerial] + 1) BETWEEN @MinSerial AND @MaxSerial
AND ([HighSerial] + 1) NOT IN (SELECT [LowSerial]
FROM [Efn]
WHERE [Mid] = @Mid)) A)
我尝试通过Linqer v4.6运行它，但它基本上从SQL窗口传递到Linq窗口。
我在Linqer中将存储过程代码剪切为此;
SELECT [HighSerial] + 1 AS 'Serial'
FROM [Efn]
WHERE [Mid] = @Mid
AND ([HighSerial] + 1) BETWEEN @MinSerial AND @MaxSerial
AND ([HighSerial] + 1) NOT IN (SELECT [LowSerial]
FROM [Efn]
WHERE [Mid] = @Mid)
Linqer在我的项目中生成了我的Linq代码;
var query = from Efn in _serialNumberContext.Efns
where
Efn.Mid == mid &&
(Efn.HighSerial + 1) >= minSerial && (Efn.HighSerial + 1) <= maxSerial &&
!
(from Efn0 in _serialNumberContext.Efns
where
Efn0.Mid == mid
select new
{
Efn0.LowSerial
}).Contains(new { LowSerial = (Int64)(Efn.HighSerial + 1) })
select new
{
Serial = (Efn.HighSerial + 1)
};
但我无法弄清楚包装T-SQL代码的Linq翻译;
SET @Target = (SELECT MIN(A.[Serial])
FROM (
...
...
...) A)
如果有帮助，我提供了有关该项目的更多细节;
Efn SQL Server Efn表包含以下字段;
[Mid] INT NOT NULL,
[Date] DATE NOT NULL,
[LowSerial] BIGINT NOT NULL,
[HighSerial] BIGINT NOT NULL
在我的项目中，我有一个Efn实体类，如下所示;
public class Efn
{
[Required]
[Column(TypeName = "int")]
public int Mid { get; set; }
[Required]
[Column(TypeName="date")]
public DateTime Date { get; set; }
[Required]
[Column(TypeName = "bigint")]
public long LowSerial { get; set; }
[Required]
[Column(TypeName = "bigint")]
public long HighSerial { get; set; }
}
这是我的dbcontext类
public class SerialNumberContext：DbContext {
public DbSet<Efn> Efns { get; set; }
public SerialNumberContext(DbContextOptions<SerialNumberContext> options) : base(options)
{
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Efn>()
.HasIndex(e => new { e.Mid, e.HighSerial, e.Date, e.LowSerial })
.IsUnique()
.HasName("IX_Efn_Mid_HighSerial_Date_LowSerial")
.ForSqlServerIsClustered();
modelBuilder.Entity<Efn>()
.HasIndex(e => new { e.Mid, e.LowSerial })
.HasName("IX_Efn_Mid_LowSerial");
base.OnModelCreating(modelBuilder);
}
}
以下是完整的旧存储过程
USE [SerialNumberDB]
GO
IF EXISTS (SELECT 1 FROM sys.objects WHERE name = N'fetchEfnSerial' AND [type]=N'P')
BEGIN
DROP PROCEDURE [dbo].[fetchEfnSerial]
END
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER OFF
GO
CREATE PROCEDURE [dbo].[fetchEfnSerial]
(
@Mid INT,
@MinSerial BIGINT = NULL,
@MaxSerial BIGINT = NULL
)
AS
DECLARE @Date DATE = CONVERT(DATE, GETDATE())
DECLARE @Target BIGINT;
DECLARE @MAX_BIG_INT BIGINT = 9223372036854775807;
IF (@MinSerial IS NULL) BEGIN SET @MinSerial = 1 END
IF (@MaxSerial IS NULL) BEGIN SET @MaxSerial = @MAX_BIG_INT END
SET @Target = NULL;
BEGIN TRY
BEGIN TRANSACTION
IF ((SELECT 1
FROM [Efn]
WHERE @MinSerial BETWEEN [LowSerial] AND [HighSerial]
AND [Mid] = @Mid) IS NULL)
BEGIN
SET @Target = @MinSerial
END
ELSE
BEGIN
SET @Target = (SELECT MIN(A.[Serial])
FROM (SELECT [HighSerial] + 1 AS 'Serial'
FROM [Efn]
WHERE [Mid] = @Mid
AND ([HighSerial] + 1) BETWEEN @MinSerial AND @MaxSerial
AND ([HighSerial] + 1) NOT IN (SELECT [LowSerial]
FROM [Efn]
WHERE [Mid] = @Mid)) A)
END
IF @Target IS NULL
BEGIN
DECLARE @ErrorText VARCHAR(255) = 'ERROR: No Serial Numbers are available in the specified range; between MinSerial: ' + CONVERT(VARCHAR(19), @MinSerial)
+ ' and MaxSerial: ' + CONVERT(VARCHAR(19), @MaxSerial)
RAISERROR (@ErrorText, 16, 1)
END
IF @Target IS NOT NULL
BEGIN
IF EXISTS (SELECT 1
FROM [Efn]
WHERE [Mid] = @Mid AND [Date] = @Date
AND [HighSerial] = @Target - 1)
BEGIN
-- If for this MID, the max value in the serial number block before the target
-- serial number is from today, just update the max serial number of that block.
UPDATE [Efn]
SET [HighSerial] = @Target
WHERE [Mid] = @Mid
AND [HighSerial] = @Target - 1
END
ELSE
BEGIN
-- Otherwise, we need to make a new serial number block for this MID for today.
INSERT INTO [Efn]
SELECT @Mid, @Date, @Target, @Target
END
-- Return the target serial number to the caller so it can be used.
SELECT @Target AS 'Serial'
END
COMMIT TRANSACTION
END TRY
BEGIN CATCH
IF (@@TRANCOUNT > 0) ROLLBACK TRANSACTION
DECLARE @ERRORMSG NVARCHAR(255)
SET @ERRORMSG = ERROR_MESSAGE()
RAISERROR(@ERRORMSG, 16, 1)
END CATCH
GO
答案 0 :(得分：3)
将SQL转换为LINQ查询理解：
DISTINCT，TOP，MIN，MAX等）转换为应用于整个LINQ查询的函数new { ... }）。LEFT JOIN使用into joinvariable 进行模拟，然后从{{1>} joinvariable 进行另一次<{1}} from替换为条件运算符（.DefaultIfEmpty()）和COALESCE测试。?:翻译为null，将IN翻译为.Contains() ... NOT IN。! low Contains() high 翻译为 low {{1 } x BETWEEN x AND high 。<=必须替换为select range_variable或者连接，一个包含所有范围变量的匿名对象。&&字段必须替换为<= ... SELECT *，以创建包含所有所需字段或表达式的匿名对象。SELECT。对于您的查询，您有3个基于3 select new {的子查询，您可以从里到外翻译它们：
}