Question

我正在使用SQLite（v1.0.88.0）和Dapper通过附加的闭包表存储一些分层数据。我在SQLite中启用了foreign_keys支持，但它对我来说根本不起作用以下是演示我的几个问题的最小示例代码：

using System.Data.SQLite;
using System.IO;
using Dapper;

class Program {
    static string db = "test.db";
    static void Main(string[] args) {
        if(!File.Exists(db))
            SQLiteConnection.CreateFile(db);
        using(SQLiteConnection c = new SQLiteConnection("Data Source=" + db)) {
            string initializationQuery =
                "PRAGMA foreign_keys = ON;" +  // enable FK
                "DROP TABLE IF EXISTS Departments;" +
                "DROP TABLE IF EXISTS Departments_treePath;" +
                "CREATE TABLE IF NOT EXISTS Departments (ID INTEGER PRIMARY KEY AUTOINCREMENT, Name TEXT);" +
                "CREATE TABLE IF NOT EXISTS Departments_treePath (ancestor INTEGER, descendant INTEGER, level INTEGER, " +
                "PRIMARY KEY (ancestor, descendant)," +
                "CONSTRAINT ancestor_ref FOREIGN KEY(ancestor) REFERENCES Departments(ID) ON DELETE CASCADE," +
                "CONSTRAINT descendant_ref FOREIGN KEY(descendant) REFERENCES Departments(ID) ON DELETE CASCADE);";
            c.Execute(initializationQuery);

            long idA = AddNode(c, 0, "A"); // ID=1
            long idB = AddNode(c, idA, "B"); // ID=2
            long idC = AddNode(c, idB, "C"); // ID=3

            // 1) It works , but it should not, because there is no ID=7 (FK fails)
            c.Execute("INSERT INTO Departments_treePath (ancestor,descendant) VALUES (7,7)");
            // 2) It works, but as far as i can see from SQLite DataBase Browser it does not delete all the references within the Departments_treePath table (cascade delete fails)
            c.Execute("DELETE FROM Departments WHERE ID=@id;", new { id = idC });
        }
    }
    static long AddNode(SQLiteConnection c, long ancestorID, string name) {
        string query = "BEGIN;" +
                       "INSERT OR ROLLBACK INTO Departments (Name) VALUES(@Name);" +
                       "CREATE TEMP TABLE _ID AS SELECT last_insert_rowid() AS id;" +
                       "INSERT INTO Departments_treePath (ancestor, descendant, level) " +
                       "SELECT t.ancestor, (SELECT id FROM _ID), t.level + 1 FROM Departments_treePath AS t " +
                       "WHERE t.descendant = @ancestor " +
                       "UNION ALL SELECT id , id, 0 FROM _ID;" +
                       "SELECT id FROM _ID; DROP TABLE _ID;" +
                       "END;";
        return System.Linq.Enumerable.First(c.Query<long>(query, new { ancestor = ancestorID, Name = name }));
    }
}

我是SQL / SQLite的新手，似乎我错过了一些东西。请指导我。

Answer 1

我有一个猜测（突然!!!）如何在演示样本中使FK工作。我立刻试了一下。而WOW，它适用于最新的Dapper / SQLite。

当然，我已经在很多年前完成了原始项目，但我相信对原始行为的清晰描述可能会对将来的某些人有所帮助。

非工作约束的原因是Dapper 在执行查询时保留连接的状态和标志。因此，当连接最初关闭时，如原始样本中那样，它将在命令执行之前再次打开，然后在完成后关闭。任何pragma都会丢失。

如果通过c.Open()打开连接，将在命令执行之间保留所有设置（这就是为什么所有的东西都适用于控制台中的@CL）。所以这是第一个和最简单的解决方案：

using(SQLiteConnection c = new SQLiteConnection("Data Source=" + db).OpenAndReturn()) {
    // ... commands
}

作为封闭连接的替代方案，您应该添加＆＃34; PRAGMA foreign_keys = ON;＆＃34;语句到每个查询：

c.Execute("PRAGMA foreign_keys = ON; INSERT INTO Departments_treePath (ancestor,descendant) VALUES (7,7)");

或强制连接级别的FK约束：

SQLiteConnection c = new SQLiteConnection("Data Source=" + db + ";foreign keys=true;")

Answer 2

对我来说，在每个语句上添加 PRAGMA foreign_keys = ON; 不起作用。

但根据 DmitryG 的解决方案：

SQLiteConnection c = new SQLiteConnection("Data Source=" + db + ";foreign keys=true;")

这奏效了。

外键约束问题（分层数据）

2 个答案: