标签：android sqlite android-sqlite auto-increment

我正在尝试使用自动递增主键的表.包括用于创建表的SQL查询.
问题是自动增量不起作用.当我插入一个NULL为NULL的行作为conversation_id的值时,它只是插入null.我在多个表上有这个问题.

-- Table: conversations
CREATE TABLE conversations (
    conversation_id INTEGER (64) PRIMARY KEY
                                 UNIQUE,
    target_id       BIGINT (64),
    sender_id       BIGINT (64),
    status          STRING (16)  NOT NULL
                                 DEFAULT unseen,
    is_group        INTEGER (1)  NOT NULL
                                 DEFAULT (0),
    last_update     INTEGER (32) DEFAULT (0),
    target_name     STRING (64),
    target_photo    STRING (256),
    unread_count    INTEGER (10) DEFAULT (0),
    last_message    STRING (256) 
);

以下是我用于插入表格的方法：

public Conversation addConversation(Conversation conversation) {
        SQLiteDatabase db = getWritableDatabase();
        ContentValues row = new ContentValues();

        row.put("target_id", conversation.getTargetID());
        row.put("sender_id", conversation.getSenderID());
        row.put("target_name", conversation.getTargetName());
        row.put("target_photo", conversation.getTargetPhoto());
        row.put("status", conversation.getStatus());
        row.put("unread_count", conversation.getUnreadCount());
        row.put("last_message", conversation.getLastMessage());

        conversation.setConversationID(db.insert(TBL_CONVERSATIONS, null, row));
        Log.d(TAG, "conversation added: "+conversation.getConversationID());

        db.close();

        return conversation;
    }

这里奇怪的是当我从insert方法中检索插入id时,它返回正确的值,但实际的数据库字段为null.

如果我理解正确声明INTEGER PRIMARY KEY的列将自动增量. [Cite]

解决方法:

来自文档：

A table created using CREATE TABLE AS has no PRIMARY KEY and no
constraints of any kind. The default value of each column is NULL.

您不必在具有PRIMARY KEY约束的COLUMN上添加UNIQUE约束.

说明：

A UNIQUE constraint is similar to a PRIMARY KEY constraint, except
that a single table may have any number of UNIQUE constraints.

而是添加NOT NULL.
这就是为什么：

According to the SQL standard, PRIMARY KEY should always imply NOT
NULL. Unfortunately, due to a bug in some early versions, this is not
the case in SQLite. Unless the column is an INTEGER PRIMARY KEY or the
table is a WITHOUT ROWID table or the column is declared NOT NULL,
SQLite allows NULL values in a PRIMARY KEY column. SQLite could be
fixed to conform to the standard, but doing so might break legacy
applications. Hence, it has been decided to merely document the fact
that SQLite allowing NULLs in most PRIMARY KEY columns.

我建议使用此列定义：

CREATE TABLE conversations (
    conversation_id INTEGER PRIMARY KEY NOT NULL AUTOINCREMENT,
...
}

标签：android,sqlite,android-sqlite,auto-increment
来源： https://codeday.me/bug/20190727/1558595.html

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