How to enable Foreign Key constraint in SQLITE with Objective C

问题

Today I noticed that Foreign key constraint on my SQLite table does not work. After reading on Stack Overflow, I found out that this should be enabled. So, I was looking for code snippet for doing that. So far, I could only find this:

[self.db executeUpdate:@"PRAGMA foreign_keys=ON"];

But this does not seem to work for me, as compiler always complains. I saw people use this line for FMDatabase type (I don't even know what is it). So, how do I enable foreign key constraint, if I open database connection like this:

- (void) openDatabase
{
    const char* databaseFile = [[self pathToDatabaseFile:@"readlater.sql"] UTF8String];
    sqlite3 *connection;
    if (sqlite3_open(databaseFile, &connection) != SQLITE_OK) {
        return;
    }
    self.db = connection;
}

Or should it be done while creating tables? Thank you.

回答1:

When you are using the SQLite C API directly, you must also use a C function to execute SQL commands:

sqlite3_exec(connection, "PRAGMA foreign_keys = on", NULL, NULL, NULL);

来源：https://stackoverflow.com/questions/24329379/how-to-enable-foreign-key-constraint-in-sqlite-with-objective-c