SQLiteDatabase执行update、insert操作的时候，conflictAlgorithm参数的含义区别

　　　/**
     * When a constraint violation occurs, an immediate ROLLBACK occurs,
     * thus ending the current transaction, and the command aborts with a
     * return code of SQLITE_CONSTRAINT. If no transaction is active
     * (other than the implied transaction that is created on every command)
     * then this algorithm works the same as ABORT.
     */
    public static final int CONFLICT_ROLLBACK = 1;

    /**
     * When a constraint violation occurs,no ROLLBACK is executed
     * so changes from prior commands within the same transaction
     * are preserved. This is the default behavior.
     */
    public static final int CONFLICT_ABORT = 2;

    /**
     * When a constraint violation occurs, the command aborts with a return
     * code SQLITE_CONSTRAINT. But any changes to the database that
     * the command made prior to encountering the constraint violation
     * are preserved and are not backed out.
     */
    public static final int CONFLICT_FAIL = 3;

    /**
     * When a constraint violation occurs, the one row that contains
     * the constraint violation is not inserted or changed.
     * But the command continues executing normally. Other rows before and
     * after the row that contained the constraint violation continue to be
     * inserted or updated normally. No error is returned.
     */
    public static final int CONFLICT_IGNORE = 4;

    /**
     * When a UNIQUE constraint violation occurs, the pre-existing rows that
     * are causing the constraint violation are removed prior to inserting
     * or updating the current row. Thus the insert or update always occurs.
     * The command continues executing normally. No error is returned.
     * If a NOT NULL constraint violation occurs, the NULL value is replaced
     * by the default value for that column. If the column has no default
     * value, then the ABORT algorithm is used. If a CHECK constraint
     * violation occurs then the IGNORE algorithm is used. When this conflict
     * resolution strategy deletes rows in order to satisfy a constraint,
     * it does not invoke delete triggers on those rows.
     * This behavior might change in a future release.
     */
    public static final int CONFLICT_REPLACE = 5;

    /**
     * Use the following when no conflict action is specified.
     */
    public static final int CONFLICT_NONE = 0;

    private static final String[] CONFLICT_VALUES = new String[]
            {"", " OR ROLLBACK ", " OR ABORT ", " OR FAIL ", " OR IGNORE ", " OR REPLACE "};

1、CONFLICT_ROLLBACK

　　当发生约束冲突时，会立即回滚，从而结束当前事务，并且命令将终止，返回代码为SQLITE_CONSTRAINT。如果没有事务处于活动状态(每个命令上创建的隐式事务除外)，则此算法的工作原理与ABORT相同。

2、CONFLICT_ABORT

　　当发生约束冲突时，不会执行回滚，因此将保留同一事务中先前命令的更改。这是默认行为。

3、CONFLICT_FAIL

　　当发生约束冲突时，该命令将使用返回代码SQLITE_CONSTRAINT中止。但是，命令在遇到违反约束之前对数据库所做的任何更改都将保留，不会被取消。

4、CONFLICT_IGNORE

　　当发生约束违反时，不插入或更改包含约束违反的一行。但是命令仍然正常执行。包含违反约束的行之前和之后的其他行将继续正常插入或更新。没有返回错误。

5、CONFLICT_REPLACE

　　当发生唯一约束违反时，在插入或更新当前行之前，将删除导致违反约束的现有行。因此，插入或更新总是发生。命令继续正常执行。没有返回错误。如果发生NOT NULL约束冲突，则该列的默认值将替换NULL值。如果列没有默认值，则使用ABORT算法。如果发生检查约束冲突，则使用忽略算法。当此冲突解决策略删除行以满足约束时，它不会对这些行调用delete触发器。这种行为在将来的版本中可能会改变。

6、CONFLICT_NONE

　　当没有指定冲突操作时，请使用以下命令。