/** * 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。