Database Mesh to visit database will form a large grid system, where they just need to be put into the right position accordingly. They are all gov‐ erned by the mesh layer. 1.1. Introduction 2 Apache ShardingSphere data from. Another challenge is that, the SQL that runs rightly in single‐node databases may not be right in the sharding database. The change of table name after sharding, or misconducts caused by operations 0-beta SHOW COLUMNS FROM t_order FROM order_ds; Schema rewrite refers to rewriting logic schema as a right and real schema found arbitrarily with unicast route. Column Derivation Column derivation in query

Database Mesh to visit databases will form a large grid system, where they just need to be put into the right positions accordingly. They are all governed by the mesh layer. 1.1. Introduction 3 Apache ShardingSphere data from. Another challenge is that, the SQL that runs rightly in single‐node databases may not be right in the sharding database. The change of table name after sharding, or misconducts caused by operations [alias] • table_reference tbl_name [AS] alias] [index_hint_list] | table_reference ([INNER] | {LEFT|RIGHT} [OUTER]) JOIN table_factor [JOIN ON conditional_expr | USING (column_list)] Subquery Stable supported

Database Mesh to visit databases will form a large grid system, where they just need to be put into the right positions accordingly. They are all governed by the mesh layer. 1.1. Introduction 3 Apache ShardingSphere data from. Another challenge is that, the SQL that runs rightly in single‐node databases may not be right in the sharding database. The change of table name after sharding, or misconducts caused by operations [alias] • table_reference tbl_name [AS] alias] [index_hint_list] | table_reference ([INNER] | {LEFT|RIGHT} [OUTER]) JOIN table_factor [JOIN ON conditional_expr | USING (column_list)] 4.3. Sharding 37 Apache

Database Mesh to visit databases will form a large grid system, where they just need to be put into the right positions accordingly. They are all governed by the mesh layer. 1.1. Introduction 3 Apache ShardingSphere data from. Another challenge is that, the SQL that runs rightly in single‐node databases may not be right in the sharding database. The change of table name after sharding, or misconducts caused by operations [alias] • table_reference tbl_name [AS] alias] [index_hint_list] | table_reference ([INNER] | {LEFT|RIGHT} [OUTER]) JOIN table_factor [JOIN ON conditional_expr | USING (column_list)] Subquery Stable supported

[alias] • table_reference tbl_name [AS] alias] [index_hint_list] | table_reference ([INNER] | {LEFT|RIGHT} [OUTER]) JOIN table_factor [JOIN ON conditional_expr | USING (column_list)] Sub-query Stable support SELECT * FROM t_order_item i RIGHT JOIN t_user_role r ON i.user_id = r.user_id 8.1. Sharding 31 Apache ShardingSphere document WHERE i.user_id = 1; SELECT * FROM t_user u RIGHT JOIN t_user_role r ON u.user_id tribute will be set to the default value on the right side of ::. 2. When neither the corresponding dynamic placeholder value nor the default value on the right side of :: exists, this attribute will be set

[alias] • table_reference tbl_name [AS] alias] [index_hint_list] | table_reference ([INNER] | {LEFT|RIGHT} [OUTER]) JOIN table_factor [JOIN ON conditional_expr | USING (column_list)] 3.1. Sharding 25 Apache WHERE i. user_id = 1; SELECT * FROM t_order_item i RIGHT JOIN t_user_role r ON i.user_id = r.user_id WHERE i.user_id = 1; SELECT * FROM t_user u RIGHT JOIN t_user_role r ON u.user_id = r.user_id WHERE acquired, so the right result cannot be acquired anyway. The right way is to rewrite pagination conditions as LIMIT 0, 3, take out all the data from the first two pages and calculate the right data based on

[alias] • table_reference tbl_name [AS] alias] [index_hint_list] | table_reference ([INNER] | {LEFT|RIGHT} [OUTER]) JOIN table_factor [JOIN ON conditional_expr | USING (column_list)] 3.1. Sharding 24 Apache WHERE i. user_id = 1; SELECT * FROM t_order_item i RIGHT JOIN t_user_role r ON i.user_id = r.user_id WHERE i.user_id = 1; SELECT * FROM t_user u RIGHT JOIN t_user_role r ON u.user_id = r.user_id WHERE acquired, so the right result cannot be acquired anyway. The right way is to rewrite pagination conditions as LIMIT 0, 3, take out all the data from the first two pages and calculate the right data based on

[alias] • table_reference tbl_name [AS] alias] [index_hint_list] | table_reference ([INNER] | {LEFT|RIGHT} [OUTER]) JOIN table_factor [JOIN ON conditional_expr | USING (column_list)] Sub-query Stable support SELECT * FROM t_order_item i RIGHT JOIN t_user_role r ON i.user_id = r.user_id 8.1. Sharding 31 Apache ShardingSphere document WHERE i.user_id = 1; SELECT * FROM t_user u RIGHT JOIN t_user_role r ON u.user_id from 90, 80, 85 and 75 already acquired, so the right result cannot be acquired anyway. 12.4. Sharding 512 Apache ShardingSphere document The right way is to rewrite pagination conditions as LIMIT

[alias] • table_reference tbl_name [AS] alias] [index_hint_list] | table_reference ([INNER] | {LEFT|RIGHT} [OUTER]) JOIN table_factor [JOIN ON conditional_expr | USING (column_list)] 4.2. 数据分片 31 Apache WHERE i. user_id = 1; SELECT * FROM t_order_item i RIGHT JOIN t_user_role r ON i.user_id = r.user_id WHERE i.user_id = 1; SELECT * FROM t_user u RIGHT JOIN t_user_role r ON u.user_id = r.user_id WHERE

[alias] • table_reference tbl_name [AS] alias] [index_hint_list] | table_reference ([INNER] | {LEFT|RIGHT} [OUTER]) JOIN table_factor [JOIN ON conditional_expr | USING (column_list)] 4.3. 数据分片 36 Apache WHERE i. user_id = 1; SELECT * FROM t_order_item i RIGHT JOIN t_user_role r ON i.user_id = r.user_id WHERE i.user_id = 1; SELECT * FROM t_user u RIGHT JOIN t_user_role r ON u.user_id = r.user_id WHERE