254 lines
9.8 KiB
Markdown
254 lines
9.8 KiB
Markdown
ALTER TABLE
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================================
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描述
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-----------
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该语句用来修改已存在的表的结构，比如：修改表及表属性、新增列、修改列及属性、删除列等。
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格式
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-----------
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```javascript
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alter_table_stmt:
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ALTER TABLE table_name
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alter_table_action_list;
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| RENAME TABLE rename_table_action_list;
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alter_table_action_list:
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alter_table_action [, alter_table_action ...]
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alter_table_action:
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ADD [COLUMN] {column_definition | (column_definition_list)}
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| CHANGE [COLUMN] column_name column_definition
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| MODIFY [COLUMN] column_definition
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| ALTER [COLUMN] column_name {SET DEFAULT const_value | DROP DEFAULT}
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| DROP [COLUMN] column_name
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| ADD [CONSTRAINT [constraint_name]] UNIQUE {INDEX | KEY} [index_name] index_desc
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| ADD {INDEX | KEY} [index_name] index_desc
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| ADD FULLTEXT [INDEX | KEY] [index_name] fulltext_index_desc
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| ALTER INDEX index_name [VISIBLE | INVISIBLE | parallel_clause]
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| DROP {INDEX | KEY} index_name
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| ADD PARTITION (range_partition_list)
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| DROP PARTITION (partition_name_list)
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| REORGANIZE PARTITION name_list INTO partition_range_or_list
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| TRUNCATE PARTITION name_list
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| [SET] table_option_list
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| RENAME [TO] table_name
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| DROP TABLEGROUP
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| DROP FOREIGN KEY fk_name
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rename_table_action_list:
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rename_table_action [, rename_table_action ...]
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rename_table_action:
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table_name TO table_name
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column_definition_list:
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column_definition [, column_definition ...]
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column_definition:
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column_name data_type
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[DEFAULT const_value] [AUTO_INCREMENT]
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[NULL | NOT NULL] [[PRIMARY] KEY] [UNIQUE [KEY]] comment
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index_desc:
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(column_desc_list) [index_type] [index_option_list]
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fulltext_index_desc:
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(column_desc_list) CTXCAT(column_desc_list) [index_option_list]
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column_desc_list:
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column_desc [, column_desc ...]
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column_desc:
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column_name [(length)] [ASC | DESC]
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index_type:
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USING BTREE
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index_option_list:
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index_option [ index_option ...]
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index_option:
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[GLOBAL | LOCAL]
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| block_size
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| compression
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| STORING(column_name_list)
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| comment
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table_option_list:
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table_option [ table_option ...]
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table_option:
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| primary_zone
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| replica_num
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| table_tablegroup
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| block_size
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| compression
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| AUTO_INCREMENT [=] INT_VALUE
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| comment
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| DUPLICATE_SCOPE [=] "none|zone|region|cluster"
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| parallel_clause
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parallel_clause:
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{NOPARALLEL | PARALLEL integer}
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partition_option:
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PARTITION BY HASH(expression)
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[subpartition_option] PARTITIONS partition_count
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| PARTITION BY KEY([column_name_list])
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[subpartition_option] PARTITIONS partition_count
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| PARTITION BY RANGE {(expression) | COLUMNS (column_name_list)}
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[subpartition_option] (range_partition_list)
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subpartition_option:
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SUBPARTITION BY HASH(expression)
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SUBPARTITIONS subpartition_count
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| SUBPARTITION BY KEY(column_name_list)
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SUBPARTITIONS subpartition_count
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| SUBPARTITION BY RANGE {(expression) | COLUMNS (column_name_list)}
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(range_subpartition_list)
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range_partition_list:
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range_partition [, range_partition ...]
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range_partition:
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PARTITION partition_name
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VALUES LESS THAN {(expression_list) | MAXVALUE}
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range_subpartition_list:
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range_subpartition [, range_subpartition ...]
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range_subpartition:
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SUBPARTITION subpartition_name
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VALUES LESS THAN {(expression_list) | MAXVALUE}
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expression_list:
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expression [, expression ...]
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column_name_list:
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column_name [, column_name ...]
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partition_name_list:
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partition_name [, partition_name ...]
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partition_count | subpartition_count:
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INT_VALUE
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```
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参数解释
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-------------
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| **参数** | **描述** |
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|---------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| ADD \[COLUMN\] | 增加列，目前不支持增加主键列。 |
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| CHANGE \[COLUMN\] | 修改列名和列属性。 |
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| MODIFY \[COLUMN\] | 修改列属性。 |
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| ALTER \[COLUMN\] | 修改列的默认值。 |
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| DROP \[COLUMN\] | 删除列，不允许删除主键列或者包含索引的列。 |
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| ADD \[UNIQUE INDEX\] | 增加唯一索引。 |
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| ADD \[INDEX\] | 增加普通索引 |
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| ALTER \[INDEX\] | 修改索引属性。 |
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| ADD \[PARTITION\] | 增加分区。 |
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| DROP \[PARTITION\] | 删除分区。 |
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| REORGANIZE \[PARTITION\] | 分区重组。 |
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| TRUNCATE \[PARTITION\] | 删除分区数据。 |
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| RENAME \[TO\] table_name | 表重命名。 |
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| DROP \[TABLEGROUP\] | 删除表组。 |
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| DROP \[FOREIGN KEY\] | 删除外键。 |
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| SET BLOCK_SIZE | 设置Partition表BLOCK大小。 |
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| SET REPLICA_NUM | 设置表的副本数（指表的副本总数）。 |
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| SET COMPRESSION | 设置表的压缩方式。 |
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| SET USE_BLOOM_FILTER | 设置是否使用BloomFilter。 |
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| SET COMMENT | 设置注释信息。 |
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| SET PROGRESSIVE_MERGE_NUM | 设置渐进合并步数，取值范围是1\~64。 |
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| parallel_clause | 指定表级别的并行度： * NOPARALLEL：并行度为1，默认配置 * PARALLEL integer：指定并行度，integer 取值大于等于 1。 |
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示例
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-----------
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* 把表 t2 的字段 d 改名为 c，并同时修改字段类型
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```javascript
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ALTER TABLE t2 CHANGE COLUMN d c CHAR(10);
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```
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* 增加、删除列
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<!-- -->
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```javascript
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ALTER TABLE test ADD c3 int;
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```
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```javascript
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ALTER TABLE test DROP c3;
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```
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* 设置表格 test 的副本数，并且增加列 c5
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```javascript
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ALTER TABLE test SET REPLICA_NUM=2, ADD COLUMN c5 INT;
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```
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* 修改表 t1 的并行度为 2
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```unknow
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ALTER TABLE t1 PARALLEL 2;
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```
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