Question

错误1064（42000）：您的SQL语法有错误;检查手册对应于您的MySQL服务器版本，以便在第1行class GameScene: SKScene { lazy var pauseButton: PauseButton = PauseButton(theTexture: pauseButtonTexture,gameScene: self) var someBool = false override func didMoveToView(view: SKView) { addChild(pauseButton) pauseButton.loadPausedLabel() } func someMethod() { } } class PauseButton: SKSpriteNode { func loadPauseLabel() { // Way 1, reference to current scene but not to specific class guard let scene = scene else { return } // Scene property is optional and is nil until button is added to a Scene so add the guard check. scene.someBool = true // NOT WORKING scene.someMethod() // NOT WORKING let label = SKLabelNode(... scene.addChild(label) // WORKING // Way 2, use "as" to cast to specific scene (e.g GameScene) so you can call properties/methods on it. This is the same as passing GameScene in the init method. guard let gameScene = scene as? GameScene else { return } // Scene property is optional and is nil until button is added to a Scene so add the guard check. // The button must be added to the scene you are trying the as? cast with, in this example GameScene. gameScene.someBool = true // WORKING gameScene.someMethod() // WORKING let label = SKLabelNode(... gameScene.addChild(label) // WORKING } }附近使用正确的语法

'(2) from empdata where empid='E-713''

如何使用MySql中的top命令获得第n个最高薪水。虽然根据我的知识我的语法是正确的，但按下输入上面的错误闪现。

Answer 1

评论时间有点长。

MySQL不支持SELECT TOP。这通常与SQL Server相关联。

支持LIMIT，所以你可以写：

delete ed
    from empdata ed
    where empid = 'E-713'
    limit 2;

但是，这非常危险，因为它删除了两个任意行。几乎在所有情况下，您都需要ORDER BY：

delete ed
    from empdata ed
    where empid = 'E-713'
    order by ??
    limit 2;

无论您使用的是TOP还是LIMIT，都是如此。

有关使用TOP命令的MySql查询

1 个答案: