SQLite foreign key problems

I've two tables that has defined as below; When i delete row from RELHOSPOL from the SQL Manager with executing a DELETE command, it nulls the necessary rows at the USER table. Whenever I delete a row from application with the method written below, it only deletes row from RELHOSPOL, and does not SET NULL the necessary rows at USER table. What is the missing point ?

CREATE TABLE [USER] (
  [ID] INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, 
  [GROUPID] INTEGER CONSTRAINT [FK_USER_GID] REFERENCES [GROUP]([ID]) ON DELETE SET NULL ON UPDATE CASCADE, 
  [HOSPITALID] INTEGER, 
  [POLIKLINIKID] INTEGER, 
  [NAME] VARCHAR(50) NOT NULL, 
  [LOGINID] VARCHAR(15) NOT NULL开发者_如何学C, 
  [EMAIL] VARCHAR(50) NOT NULL, 
  [PASSWORD] VARCHAR(32) NOT NULL, 
  CONSTRAINT [FK_USER_RELHOSPOL] FOREIGN KEY([HOSPITALID], [POLIKLINIKID]) REFERENCES [RELHOSPOL]([HOSPITALID], [POLIKLINIKID]) ON DELETE SET NULL ON UPDATE CASCADE);

CREATE UNIQUE INDEX [AS] ON [USER] ([LOGINID]);
CREATE UNIQUE INDEX [AS1] ON [USER] ([EMAIL]));

CREATE TABLE [RELHOSPOL] (
  [ID] INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, 
  [HOSPITALID] INTEGER, 
  [POLIKLINIKID] INTEGER);

CREATE UNIQUE INDEX [UNIQUE_RELHOSPOL] ON [RELHOSPOL] ([HOSPITALID], [POLIKLINIKID]);

public void deletePoliklinikFromHospital(int hospitalId, int poliklinikId) throws SQLException{

        String query = "DELETE FROM [RELHOSPOL] WHERE (HOSPITALID = ? AND POLIKLINIKID = ?)";
        try {
            PreparedStatement statement = db.prepareStatement(query);
            statement.setInt(1, hospitalId);
            statement.setInt(2, poliklinikId);
            statement.executeUpdate();
        } catch (SQLException e) {
            throw new SQLException(e.getMessage());
        }
    }

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You need to turn on enforcement of foreign keys, which is off by default for reasons of backward compatibility. It's a per-connection configuration option. Add this as one of the first things you do once you've made a Connection:

PRAGMA foreign_keys = on;