unit-testing - 具有内存存储的核心数据堆栈的单元测试不断失败-6ren

unit-testing - 具有内存存储的核心数据堆栈的单元测试不断失败

转载作者：行者123 更新时间：2023-12-03 21:27:03

我正在建立一个个人项目，让我和我的妻子监控我们的杂货消费习惯。该应用程序使用了 Core Data，我在进行单元测试时遇到了困难。我正在测试我的 CoreDataStack类以确保其方法正在保存和删除对象。

这是CoreDataStack :

internal class CoreDataStack {

    // MARK: - Properties

    private let modelName: String

    internal lazy var storeContainer: NSPersistentContainer = {
        let container = NSPersistentContainer(name: self.modelName)
        container.loadPersistentStores { (storeDescription, error) in
            if let error = error as NSError? {
                fatalError("Unresolved error \(error), \(error.userInfo)")
            }
        }
        return container
    }()

    internal lazy var managedContext: NSManagedObjectContext = {
        return self.storeContainer.viewContext
    }()

    // MARK: - Initialization

    internal init(modelName: String = "Cart") {
        self.modelName = modelName
    }

    // MARK: - Saving

    internal func saveContext() {
        guard managedContext.hasChanges else {
            return
        }
        do {
            try managedContext.save()
        } catch let error as NSError {
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }
    }

    // MARK: - Deleting

    internal func delete(object: NSManagedObject, from context: NSManagedObjectContext) {
        context.delete(object)
    }

    internal func delete(allObjectsForEntity entity: String, from context: NSManagedObjectContext) {
        let deleteFetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entity)
        let batchDeleteRequest = NSBatchDeleteRequest(fetchRequest: deleteFetchRequest)
        do {
            try storeContainer.persistentStoreCoordinator.execute(batchDeleteRequest, with: context)
        } catch let error as NSError {
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }
    }

}

我创建了一个 CoreDataStack 的子类，称为 TestCoreDataStack ，在我的测试目标中。 TestCoreDataStack使用内存存储，以便在包含测试完成时将其销毁。

这是 TestCoreDataStack :

internal final class TestCoreDataStack: CoreDataStack {

    // MARK: - Initialization

    internal override init(modelName: String = "Cart") {
        super.init(modelName: modelName)
        let persistentStoreDescription = NSPersistentStoreDescription()
        persistentStoreDescription.type = NSInMemoryStoreType
        let container = NSPersistentContainer(name: modelName)
        container.persistentStoreDescriptions = [persistentStoreDescription]
        container.loadPersistentStores { (storeDescription, error) in
            if let error = error as NSError? {
                fatalError("Unresolved error \(error), \(error.userInfo)")
            }
        }
        self.storeContainer = container
    } 
}

我也有一个助手类， ManagedObjectFetcher ，仅包含在我的测试目标中，仅用于在保存或删除托管对象后获取托管对象。使用此类以便我可以验证计数以及在保存或删除对象后是否存在正确的信息。

她的是 ManagedObjectFetcher :

internal final class ManagedObjectFetcher {

    // MARK: - Properties

    private let coreDataStack: CoreDataStack

    // MARK: - Initialization

    internal init(coreDataStack: CoreDataStack) {
        self.coreDataStack = coreDataStack
    }

    // MARK: - All Records

    internal func allRecords<T: NSManagedObject>(for entity : T.Type) -> [T] {
        let request = T.fetchRequest()
        do {
            guard let results = try coreDataStack.managedContext.fetch(request) as? [T] else {
                fatalError("Invalid results")
            }
            return results
        } catch {
            fatalError("Error with request: \(error)")
        }
    }

}

CoreDataStackTests是我的 XCTestCase用于测试的子类 CoreDataStack以确保对象被保存或删除。

这是 CoreDataStackTests :

internal final class CoreDataStackTests: XCTestCase {

    // MARK: - Properties

    private var coreDataStack: TestCoreDataStack!

    private var managedObjectFetcher: ManagedObjectFetcher!

    // MARK: - Test Lifecycle

    override func setUp() {
        super.setUp()
        coreDataStack = TestCoreDataStack()
        managedObjectFetcher = ManagedObjectFetcher(coreDataStack: coreDataStack)
    }

    override func tearDown() {
        coreDataStack = nil
        managedObjectFetcher = nil
        super.tearDown()
    }

    // MARK: - Saving

    // Test 1
    internal func test_CoreDataStack_Saves_GroceryItem() {
        let preResults = managedObjectFetcher.allRecords(for: GroceryItem.self)
        XCTAssertEqual(preResults.count, 0, "Expected `0`")
        let _ = GroceryItem(name: "Name", singleItemPrice: Decimal(0.99), quantity: 1, date: Date(), isTaxable: true, managedObjectContext: coreDataStack.managedContext)
        coreDataStack.saveContext()
        let postResults = managedObjectFetcher.allRecords(for: GroceryItem.self)
        XCTAssertEqual(postResults.count, 1, "Expected `1`")
    }

    // MARK: - Deleting

    // Test 2
    internal func test_CoreDataStack_Deletes_GroceryItem() {
        let initialResults = managedObjectFetcher.allRecords(for: GroceryItem.self)
        XCTAssertEqual(initialResults.count, 0, "Expected `0`")
        let item = GroceryItem(name: "Name", singleItemPrice: Decimal(0.99), quantity: 1, date: Date(), isTaxable: true, managedObjectContext: coreDataStack.managedContext)
        coreDataStack.saveContext()
        let preResults = managedObjectFetcher.allRecords(for: GroceryItem.self)
        XCTAssertEqual(preResults.count, 1, "Expected `1`")
        coreDataStack.delete(object: item, from: coreDataStack.managedContext)
        coreDataStack.saveContext()
        let postResults = managedObjectFetcher.allRecords(for: GroceryItem.self)
        XCTAssertEqual(postResults.count, 0, "Expected `0`")
    }

    // Test 3
    internal func test_CoreDataStack_Deletes_AllGroceryItems() {
        let initialResults = managedObjectFetcher.allRecords(for: GroceryItem.self)
        XCTAssertEqual(initialResults.count, 0, "Expected `0`")
        let _ = GroceryItem(name: "Name", singleItemPrice: Decimal(0.99), quantity: 1, date: Date(), isTaxable: true, managedObjectContext: coreDataStack.managedContext)
        let _ = GroceryItem(name: "Another Name", singleItemPrice: Decimal(5.99), quantity: 2, date: Date(), isTaxable: false, managedObjectContext: coreDataStack.managedContext)
        coreDataStack.saveContext()
        let preResults = managedObjectFetcher.allRecords(for: GroceryItem.self)
        XCTAssertEqual(preResults.count, 2, "Expected `2`")
        coreDataStack.delete(allObjectsForEntity: GroceryItem.description(), from: coreDataStack.managedContext)
        coreDataStack.saveContext()
        let postResults = managedObjectFetcher.allRecords(for: GroceryItem.self)
        XCTAssertEqual(postResults.count, 0, "Expected `0`")
    }

}

在 CoreDataStackTests 中执行测试时，我遇到了以下无法解决的问题:

测试 1:单独运行时测试通过。当CoreDataStack的所有测试运行测试，它通过或失败。

测试 2:单独运行时测试通过。当CoreDataStack的所有测试运行测试，它通过或失败。

测试 3:无论是单独运行还是与其他测试一起运行，该测试都不会通过。测试失败断点在 try storeContainer.persistentStoreCoordinator.execute(batchDeleteRequest, with: context) 处被击中内delete(allObjectsForEntity entity: String, from context: NSManagedObjectContext) CoreDataStack的方法每次运行。

这是我在运行所有三个测试后得到的控制台输出:

Test Suite 'Selected tests' started at 2017-07-03 21:24:01.609
Test Suite 'CartTests.xctest' started at 2017-07-03 21:24:01.610
Test Suite 'CoreDataStackTests' started at 2017-07-03 21:24:01.610
Test Case '-[CartTests.CoreDataStackTests test_CoreDataStack_Deletes_AllGroceryItems]' started.
<unknown>:0: error: -[CartTests.CoreDataStackTests test_CoreDataStack_Deletes_AllGroceryItems] : failed: caught "NSInternalInconsistencyException", "Unknown command type <NSBatchDeleteRequest : resultType : 0, fetch :<NSFetchRequest: 0x6000000de450> (entity: GroceryItem; predicate: ((null)); sortDescriptors: ((null)); type: NSManagedObjectIDResultType; includesPropertyValues: NO; includesPendingChanges: NO; ) >"
(
    0   CoreFoundation                      0x000000010c90079b __exceptionPreprocess + 171
    1   libobjc.A.dylib                     0x000000010bd2e121 objc_exception_throw + 48
    2   CoreData                            0x000000010c34febf -[NSMappedObjectStore executeRequest:withContext:error:] + 303
    3   CoreData                            0x000000010c3f0f6d __65-[NSPersistentStoreCoordinator executeRequest:withContext:error:]_block_invoke + 2509
    4   CoreData                            0x000000010c3e9126 __55-[NSPersistentStoreCoordinator _routeHeavyweightBlock:]_block_invoke + 86
    5   CoreData                            0x000000010c3fcda9 gutsOfBlockToNSPersistentStoreCoordinatorPerform + 185
    6   libdispatch.dylib                   0x0000000110bfbbb9 _dispatch_client_callout + 8
    7   libdispatch.dylib                   0x0000000110c02500 _dispatch_queue_barrier_sync_invoke_and_complete + 92
    8   CoreData                            0x000000010c3e8ab5 _perform + 213
    9   CoreData                            0x000000010c3e8e3b -[NSPersistentStoreCoordinator _routeHeavyweightBlock:] + 283
    10  CoreData                            0x000000010c2f2aba -[NSPersistentStoreCoordinator executeRequest:withContext:error:] + 634
    11  Cart                                0x000000010b40b667 _T04Cart13CoreDataStackC16deleteAllObjectsySS9forEntity_So22NSManagedObjectContextC4fromtF + 391
    12  CartTests                           0x00000001240ea070 _T09CartTests013CoreDataStackB0C05test_cdE24_Deletes_AllGroceryItemsyyF + 3344
    13  CartTests                           0x00000001240eabc4 _T09CartTests013CoreDataStackB0C05test_cdE24_Deletes_AllGroceryItemsyyFTo + 36
    14  CoreFoundation                      0x000000010c884f8c __invoking___ + 140
    15  CoreFoundation                      0x000000010c884e60 -[NSInvocation invoke] + 320
    16  XCTest                              0x00000001224dd6e0 __24-[XCTestCase invokeTest]_block_invoke_2 + 451
    17  XCTest                              0x0000000122524bed -[XCUITestContext performInScope:] + 187
    18  XCTest                              0x00000001224dd4f8 -[XCTestCase invokeTest] + 254
    19  XCTest                              0x00000001224de424 __26-[XCTestCase performTest:]_block_invoke.362 + 42
    20  XCTest                              0x0000000122529432 +[XCTContext runInContextForTestCase:block:] + 163
    21  XCTest                              0x00000001224dddc0 -[XCTestCase performTest:] + 608
    22  XCTest                              0x00000001224da396 __27-[XCTestSuite performTest:]_block_invoke + 295
    23  XCTest                              0x00000001224d9f8d -[XCTestSuite _performProtectedSectionForTest:testSection:] + 26
    24  XCTest                              0x00000001224da171 -[XCTestSuite performTest:] + 214
    25  XCTest                              0x00000001224da396 __27-[XCTestSuite performTest:]_block_invoke + 295
    26  XCTest                              0x00000001224d9f8d -[XCTestSuite _performProtectedSectionForTest:testSection:] + 26
    27  XCTest                              0x00000001224da171 -[XCTestSuite performTest:] + 214
    28  XCTest                              0x00000001224da396 __27-[XCTestSuite performTest:]_block_invoke + 295
    29  XCTest                              0x00000001224d9f8d -[XCTestSuite _performProtectedSectionForTest:testSection:] + 26
    30  XCTest                              0x00000001224da171 -[XCTestSuite performTest:] + 214
    31  XCTest                              0x0000000122530625 __44-[XCTTestRunSession runTestsAndReturnError:]_block_invoke + 40
    32  XCTest                              0x00000001224ecb99 -[XCTestObservationCenter _observeTestExecutionForBlock:] + 480
    33  XCTest                              0x00000001225304c4 -[XCTTestRunSession runTestsAndReturnError:] + 281
    34  XCTest                              0x00000001224c9d43 -[XCTestDriver runTestsAndReturnError:] + 254
    35  XCTest                              0x00000001225286b7 _XCTestMain + 616
    36  CoreFoundation                      0x000000010c8a3dcc __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
    37  CoreFoundation                      0x000000010c88833b __CFRunLoopDoBlocks + 203
    38  CoreFoundation                      0x000000010c887b34 __CFRunLoopRun + 1060
    39  CoreFoundation                      0x000000010c887499 CFRunLoopRunSpecific + 409
    40  GraphicsServices                    0x00000001121d79d7 GSEventRunModal + 62
    41  UIKit                               0x000000010cd7f0b8 UIApplicationMain + 159
    42  Cart                                0x000000010b40e637 main + 55
    43  libdyld.dylib                       0x0000000110c71771 start + 1
    44  ???                                 0x0000000000000005 0x0 + 5
)
Test Case '-[CartTests.CoreDataStackTests test_CoreDataStack_Deletes_AllGroceryItems]' failed (2636.006 seconds).
Test Case '-[CartTests.CoreDataStackTests test_CoreDataStack_Deletes_GroceryItem]' started.
<unknown>:0: error: -[CartTests.CoreDataStackTests test_CoreDataStack_Deletes_GroceryItem] : failed: caught "NSInvalidArgumentException", "executeFetchRequest:error: <null> is not a valid NSFetchRequest."
(
    0   CoreFoundation                      0x000000010c90079b __exceptionPreprocess + 171
    1   libobjc.A.dylib                     0x000000010bd2e121 objc_exception_throw + 48
    2   CoreData                            0x000000010c2f11d8 -[NSManagedObjectContext executeFetchRequest:error:] + 792
    3   CartTests                           0x00000001240eb1f7 _T09CartTests20ManagedObjectFetcherC10allRecordsSayxGxm3for_tSo09NSManagedD0CRbzlF + 247
    4   CartTests                           0x00000001240e7d86 _T09CartTests013CoreDataStackB0C05test_cdE20_Deletes_GroceryItemyyF + 182
    5   CartTests                           0x00000001240e9344 _T09CartTests013CoreDataStackB0C05test_cdE20_Deletes_GroceryItemyyFTo + 36
    6   CoreFoundation                      0x000000010c884f8c __invoking___ + 140
    7   CoreFoundation                      0x000000010c884e60 -[NSInvocation invoke] + 320
    8   XCTest                              0x00000001224dd6e0 __24-[XCTestCase invokeTest]_block_invoke_2 + 451
    9   XCTest                              0x0000000122524bed -[XCUITestContext performInScope:] + 187
    10  XCTest                              0x00000001224dd4f8 -[XCTestCase invokeTest] + 254
    11  XCTest                              0x00000001224de424 __26-[XCTestCase performTest:]_block_invoke.362 + 42
    12  XCTest                              0x0000000122529432 +[XCTContext runInContextForTestCase:block:] + 163
    13  XCTest                              0x00000001224dddc0 -[XCTestCase performTest:] + 608
    14  XCTest                              0x00000001224da396 __27-[XCTestSuite performTest:]_block_invoke + 295
    15  XCTest                              0x00000001224d9f8d -[XCTestSuite _performProtectedSectionForTest:testSection:] + 26
    16  XCTest                              0x00000001224da171 -[XCTestSuite performTest:] + 214
    17  XCTest                              0x00000001224da396 __27-[XCTestSuite performTest:]_block_invoke + 295
    18  XCTest                              0x00000001224d9f8d -[XCTestSuite _performProtectedSectionForTest:testSection:] + 26
    19  XCTest                              0x00000001224da171 -[XCTestSuite performTest:] + 214
    20  XCTest                              0x00000001224da396 __27-[XCTestSuite performTest:]_block_invoke + 295
    21  XCTest                              0x00000001224d9f8d -[XCTestSuite _performProtectedSectionForTest:testSection:] + 26
    22  XCTest                              0x00000001224da171 -[XCTestSuite performTest:] + 214
    23  XCTest                              0x0000000122530625 __44-[XCTTestRunSession runTestsAndReturnError:]_block_invoke + 40
    24  XCTest                              0x00000001224ecb99 -[XCTestObservationCenter _observeTestExecutionForBlock:] + 480
    25  XCTest                              0x00000001225304c4 -[XCTTestRunSession runTestsAndReturnError:] + 281
    26  XCTest                              0x00000001224c9d43 -[XCTestDriver runTestsAndReturnError:] + 254
    27  XCTest                              0x00000001225286b7 _XCTestMain + 616
    28  CoreFoundation                      0x000000010c8a3dcc __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
    29  CoreFoundation                      0x000000010c88833b __CFRunLoopDoBlocks + 203
    30  CoreFoundation                      0x000000010c887b34 __CFRunLoopRun + 1060
    31  CoreFoundation                      0x000000010c887499 CFRunLoopRunSpecific + 409
    32  GraphicsServices                    0x00000001121d79d7 GSEventRunModal + 62
    33  UIKit                               0x000000010cd7f0b8 UIApplicationMain + 159
    34  Cart                                0x000000010b40e637 main + 55
    35  libdyld.dylib                       0x0000000110c71771 start + 1
    36  ???                                 0x0000000000000005 0x0 + 5
)
Test Case '-[CartTests.CoreDataStackTests test_CoreDataStack_Deletes_GroceryItem]' failed (11.969 seconds).
Test Case '-[CartTests.CoreDataStackTests test_CoreDataStack_Saves_GroceryItem]' started.
<unknown>:0: error: -[CartTests.CoreDataStackTests test_CoreDataStack_Saves_GroceryItem] : failed: caught "NSInvalidArgumentException", "executeFetchRequest:error: <null> is not a valid NSFetchRequest."
(
    0   CoreFoundation                      0x000000010c90079b __exceptionPreprocess + 171
    1   libobjc.A.dylib                     0x000000010bd2e121 objc_exception_throw + 48
    2   CoreData                            0x000000010c2f11d8 -[NSManagedObjectContext executeFetchRequest:error:] + 792
    3   CartTests                           0x00000001240eb1f7 _T09CartTests20ManagedObjectFetcherC10allRecordsSayxGxm3for_tSo09NSManagedD0CRbzlF + 247
    4   CartTests                           0x00000001240e6fe6 _T09CartTests013CoreDataStackB0C05test_cdE18_Saves_GroceryItemyyF + 182
    5   CartTests                           0x00000001240e7cb4 _T09CartTests013CoreDataStackB0C05test_cdE18_Saves_GroceryItemyyFTo + 36
    6   CoreFoundation                      0x000000010c884f8c __invoking___ + 140
    7   CoreFoundation                      0x000000010c884e60 -[NSInvocation invoke] + 320
    8   XCTest                              0x00000001224dd6e0 __24-[XCTestCase invokeTest]_block_invoke_2 + 451
    9   XCTest                              0x0000000122524bed -[XCUITestContext performInScope:] + 187
    10  XCTest                              0x00000001224dd4f8 -[XCTestCase invokeTest] + 254
    11  XCTest                              0x00000001224de424 __26-[XCTestCase performTest:]_block_invoke.362 + 42
    12  XCTest                              0x0000000122529432 +[XCTContext runInContextForTestCase:block:] + 163
    13  XCTest                              0x00000001224dddc0 -[XCTestCase performTest:] + 608
    14  XCTest                              0x00000001224da396 __27-[XCTestSuite performTest:]_block_invoke + 295
    15  XCTest                              0x00000001224d9f8d -[XCTestSuite _performProtectedSectionForTest:testSection:] + 26
    16  XCTest                              0x00000001224da171 -[XCTestSuite performTest:] + 214
    17  XCTest                              0x00000001224da396 __27-[XCTestSuite performTest:]_block_invoke + 295
    18  XCTest                              0x00000001224d9f8d -[XCTestSuite _performProtectedSectionForTest:testSection:] + 26
    19  XCTest                              0x00000001224da171 -[XCTestSuite performTest:] + 214
    20  XCTest                              0x00000001224da396 __27-[XCTestSuite performTest:]_block_invoke + 295
    21  XCTest                              0x00000001224d9f8d -[XCTestSuite _performProtectedSectionForTest:testSection:] + 26
    22  XCTest                              0x00000001224da171 -[XCTestSuite performTest:] + 214
    23  XCTest                              0x0000000122530625 __44-[XCTTestRunSession runTestsAndReturnError:]_block_invoke + 40
    24  XCTest                              0x00000001224ecb99 -[XCTestObservationCenter _observeTestExecutionForBlock:] + 480
    25  XCTest                              0x00000001225304c4 -[XCTTestRunSession runTestsAndReturnError:] + 281
    26  XCTest                              0x00000001224c9d43 -[XCTestDriver runTestsAndReturnError:] + 254
    27  XCTest                              0x00000001225286b7 _XCTestMain + 616
    28  CoreFoundation                      0x000000010c8a3dcc __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
    29  CoreFoundation                      0x000000010c88833b __CFRunLoopDoBlocks + 203
    30  CoreFoundation                      0x000000010c887b34 __CFRunLoopRun + 1060
    31  CoreFoundation                      0x000000010c887499 CFRunLoopRunSpecific + 409
    32  GraphicsServices                    0x00000001121d79d7 GSEventRunModal + 62
    33  UIKit                               0x000000010cd7f0b8 UIApplicationMain + 159
    34  Cart                                0x000000010b40e637 main + 55
    35  libdyld.dylib                       0x0000000110c71771 start + 1
    36  ???                                 0x0000000000000005 0x0 + 5
)
Test Case '-[CartTests.CoreDataStackTests test_CoreDataStack_Saves_GroceryItem]' failed (4.826 seconds).
Test Suite 'CoreDataStackTests' failed at 2017-07-03 22:08:14.412.
 Executed 3 tests, with 3 failures (3 unexpected) in 2652.801 (2652.802) seconds
Test Suite 'CartTests.xctest' failed at 2017-07-03 22:08:14.413.
 Executed 3 tests, with 3 failures (3 unexpected) in 2652.801 (2652.803) seconds
Test Suite 'Selected tests' failed at 2017-07-03 22:08:14.413.
 Executed 3 tests, with 3 failures (3 unexpected) in 2652.801 (2652.804) seconds


Test session log:

/var/folders/n9/48n8p_ms6rs2yc8vdkhq89br0000gn/T/com.apple.dt.XCTest/IDETestRunSession-44B21AFF-A887-42A9-8EF0-23B48DBC4744/CartTests-4BFEF3B5-D9B6-47D9-BA80-6007A7991D19/Session-CartTests-2017-07-03_212349-pZbWPl.log

我做错了什么导致这些测试失败？

最佳答案

不幸的是，batch deletes are not supported with CoreData in-memory stores :

Important: Batch deletes are only available when you are using a SQLite persistent store.

关于unit-testing - 具有内存存储的核心数据堆栈的单元测试不断失败，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/44887539/

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c - 具有 `for` 循环的菱形输出
该程序只是在用户输入行数时创建菱形的形状，因此它有 6 个 for 循环； 3 个循环创建第一个三角形，3 个循环创建另一个三角形，通过这 2 个三角形和 6 个循环，我们得到了一个菱形，这是整个程序
c# - 具有 "&"的查询字符串值
我有一个像这样的查询字符串 www.google.com?Department=Education & Finance&Department=Health 我有这些 li 标签，它们的查询字符串是这样
c# - 具有/不同配置值的单元测试静态构造函数
我有一个带有静态构造函数的类，我用它来读取 app.config 值。如何使用不同的配置值对类进行单元测试。我正在考虑在不同的应用程序域中运行每个测试，这样我就可以为每个测试执行静态构造函数 - 但我
c++ - 具有 OR 搜索功能的多键容器
我正在寻找一个可以容纳多个键的容器，如果我为其中一个键值输入保留值(例如 0)，它会被视为“或”搜索。 map, int > myContainer; myContainer.insert(make_
mysql - 具有/多种类型的单个对象的关系表设计
我正在为 Web 应用程序创建数据库，并正在寻找一些建议来对可能具有多种类型的单个实体进行建模，每种类型具有不同的属性。作为示例，假设我想为“数据源”对象创建一个关系模型。所有数据源都会有一些共享属
arrays - 具有 IN 条件的存储过程语法
(1) =>CREATE TABLE T1(id BIGSERIAL PRIMARY KEY, name TEXT); CREATE TABLE (2) =>INSERT INTO T1 (name)
sql - 具有 AS 别名的不明确列引用
我不确定在使用别名时如何解决不明确的列引用。假设有两个表，a 和 b，它们都有一个 name 列。如果我加入这两个表并为结果添加别名，我不知道如何为这两个表引用 name 列。我已经尝试了一些变体，
mysql - 具有 IN 条件的自定义订单
我的查询是: select * from table where id IN (1,5,4,3,2) 我想要的与这个顺序完全相同，不是从1...5，而是从1,5,4,3,2。我怎样才能做到这一点？最
c# - 具有@符号的列名
我正在使用 C# 代码执行动态生成的 MySQL 查询。抛出异常: CREATE TABLE dump ("@employee_OID" VARCHAR(50)); "{"You have an er
java - 具有 + 号的日期格式问题
我有日期 2016-03-30T23:59:59.000000+0000。我可以知道它的格式是什么吗？因为如果我使用 yyyy-MM-dd'T'HH:mm:ss.SSS，它会抛出异常最佳答案 Sim
MYSQL - 具有 in 子句的删除查询中的语法错误
我有一个示例模式，它的 SQL Fiddle 如下: http://sqlfiddle.com/#!2/6816b/2 这个 fiddle 只是根据 where 子句中的条件查询示例数据库，如下所示:

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unit-testing - 具有内存存储的核心数据堆栈的单元测试不断失败