java - JPQL：在更新中将列设置为空

Question

以下 JPQL：

UPDATE SignIn signIn SET signIn.cookieUUID = null WHERE signIn.user.id = :userID

由于“= null”，给我以下错误：

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'IS NULL WHERE `B0`.`ID` = 9' at line 1
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)

但是当我将字段设置为空字符串（=''）时它会起作用。

那么如何使用 JQPL 将列设置为空？

Answer 1

我认为它NULL（大写）::Reference JPQL and Eclipselink

 UPDATE SignIn signIn SET signIn.cookieUUID = NULL WHERE signIn.user.id = :userID

或使用参数查询：

     String sQuery = "UPDATE SignIn signIn SET signIn.cookieUUID = :cookieUUID "+
                 "WHERE signIn.user.id = :userID";
     Query query= entityManager.createQuery(sQuery );
     query.setParameter("cookieUUID", null);
     query.setParameter("userID", userID);
     query.executeUpdate();