according to sorting conditions after merging. For example, if the SQL is: SELECT score FROM t_score ORDER BY score DESC LIMIT 1, 2; The following picture shows the pagination execution results without by score common in both tables, and they are supposed to be 95 and 90. Since the executed SQL can only acquire the second and the third piece of data from each table, i.e., 90 and 80 from t_score_0, 85 and 75 from t_score_1. When merging results, it can only merge from 90, 80, 85 and 75 already acquired, so the right result cannot be acquired anyway. The right way is to rewrite pagination conditions

according to sorting conditions after merging. For example, if the SQL is: SELECT score FROM t_score ORDER BY score DESC LIMIT 1, 2; The following picture shows the pagination execution results without by score common in both tables, and they are supposed to be 95 and 90. Since the executed SQL can only acquire the second and the third piece of data from each table, i.e., 90 and 80 from t_score_0, 85 and 75 from t_score_1. When merging results, it can only merge from 90, 80, 85 and 75 already acquired, so the right result cannot be acquired anyway. The right way is to rewrite pagination conditions

according to sorting conditions after merging. For example, if the SQL is: SELECT score FROM t_score ORDER BY score DESC LIMIT 1, 2; The following picture shows the pagination execution results without by score common in both tables, and they are supposed to be 95 and 90. Since the executed SQL can only acquire the second and the third piece of data from each table, i.e., 90 and 80 from t_score_0, 85 and 75 from t_score_1. When merging results, it can only merge from 90, 80, 85 and 75 already acquired, so the right result cannot be acquired anyway. The right way is to rewrite pagination conditions

data according to sorting conditions after merging. For example, if SQL is: SELECT score FROM t_score ORDER BY score DESC LIMIT 1, 2; The following picture shows the pagination execution results without sorted by score in both tables, and they are supposed to be 95 and 90. Since executed SQL can only acquire the second and the third piece of data from each table, i.e., 90 and 80 from t_score_0, 85 and and 75 from t_score_1. When merging results, it can only merge from 90, 7.4. Sharding 373 Apache ShardingSphere document, v5.2.0 80, 85 and 75 already acquired, so the right result cannot be acquired

according to sorting conditions after merging. For example, if the SQL is: SELECT score FROM t_score ORDER BY score DESC LIMIT 1, 2; The following picture shows the pagination execution results without by score common in both tables, and they are supposed to be 95 and 90. Since the executed SQL can only acquire the second and the third piece of data from each table, i.e., 90 and 80 from t_score_0, 85 and 75 from t_score_1. When merging results, it can only merge from 90, 80, 85 and 75 already acquired, so the right result cannot be acquired anyway. The right way is to rewrite pagination conditions

data according to sorting conditions after merging. For example, if SQL is: SELECT score FROM t_score ORDER BY score DESC LIMIT 1, 2; The following picture shows the pagination execution results without sorted by score in both tables, and they are supposed to be 95 and 90. Since executed SQL can only acquire the second and the third piece of data from each table, i.e., 90 and 80 from t_score_0, 85 and and 75 from t_score_1. When merging results, it can only merge from 90, 7.4. Sharding 400 Apache ShardingSphere document, v5.2.1 80, 85 and 75 already acquired, so the right result cannot be acquired

data according to sorting conditions after merging. For example, if SQL is: SELECT score FROM t_score ORDER BY score DESC LIMIT 1, 2; The following picture shows the pagination execution results without sorted by score in both tables, and they are supposed to be 95 and 90. Since executed SQL can only acquire the second and the third piece of data from each table, i.e., 90 and 80 from t_score_0, 85 and and 75 from t_score_1. When merging results, it can only merge from 90, 80, 85 and 75 already acquired, so the right result cannot be acquired anyway. 12.4. Sharding 512 Apache ShardingSphere document

data according to sorting conditions after merging. For example, if SQL is: SELECT score FROM t_score ORDER BY score DESC LIMIT 1, 2; The following picture shows the pagination execution results without sorted by score in both tables, and they are supposed to be 95 and 90. Since executed SQL can only acquire the second and the third piece of data from each table, i.e., 90 and 80 from t_score_0, 85 and and 75 from t_score_1. When merging results, it can only merge from 90, 80, 85 and 75 already acquired, so the right result cannot be acquired anyway. 12.4. Sharding 541 Apache ShardingSphere document

SQL 为： SELECT score FROM t_score ORDER BY score DESC LIMIT 1, 2; 下图展示了不进行 SQL 的改写的分页执行结果。 通过图中所示，想要取得两个表中共同的按照分数排序的第 2 条和第 3 条数据，应该是 95 和 90。由于执 行的 SQL 只能从每个表中获取第 2 条和第 3 条数据，即从 t_score_0 表中获取的是 90 和 和 80；从 t_score_1 表中获取的是 85 和 75。因此进行结果归并时，只能从获取的 90，80，85 和 75 之中进行归并，那么结 果归并无论怎么实现，都不可能获得正确的结果。 正确的做法是将分页条件改写为 LIMIT 0, 3，取出所有前两页数据，再结合排序条件计算出正确的数 据。下图展示了进行 SQL 改写之后的分页执行结果。 3.1. 数据分片 34 Apache 级队列，t_score_0 的第一个数据值 最大，t_score_2 的第一个数据值次之，t_score_1 的第一个数据值最小，因此优先级队列根据 t_score_0， t_score_2 和 t_score_1 的方式排序队列。 下图则展现了进行 next 调用的时候，排序归并是如何进行的。通过图中我们可以看到，当进行第一次 next 调用时，排在队列首位的 t_score_0 将会被

SQL 为： SELECT score FROM t_score ORDER BY score DESC LIMIT 1, 2; 下图展示了不进行 SQL 的改写的分页执行结果。 通过图中所示，想要取得两个表中共同的按照分数排序的第 2 条和第 3 条数据，应该是 95 和 90。由于执 行的 SQL 只能从每个表中获取第 2 条和第 3 条数据，即从 t_score_0 表中获取的是 90 和 和 80；从 t_score_1 表中获取的是 85 和 75。因此进行结果归并时，只能从获取的 90，80，85 和 75 之中进行归并，那么结 果归并无论怎么实现，都不可能获得正确的结果。 正确的做法是将分页条件改写为 LIMIT 0, 3，取出所有前两页数据，再结合排序条件计算出正确的数 据。下图展示了进行 SQL 改写之后的分页执行结果。 7.1. 数据分片 237 Apache 级队列，t_score_0 的第一个数据值 最大，t_score_2 的第一个数据值次之，t_score_1 的第一个数据值最小，因此优先级队列根据 t_score_0， t_score_2 和 t_score_1 的方式排序队列。 下图则展现了进行 next 调用的时候，排序归并是如何进行的。通过图中我们可以看到，当进行第一次 next 调用时，排在队列首位的 t_score_0 将会被