Clickhouse的列操作
ALTER TABLE [db].name [ON CLUSTER cluster] ADD|DROP|CLEAR|COMMENT|MODIFY COLUMN ...
在查詢中,指定一個或多個逗號分隔操作的列表。
每個操作都是對列的操作。
支持以下操作:
- ADD COLUMN — Adds a new column to the table.
- DROP COLUMN — Deletes the column.
- CLEAR COLUMN — Resets column values.
- COMMENT COLUMN — Adds a text comment to the column.
- MODIFY COLUMN — Changes column's type, default expression and TTL.
下面詳細描述這些動作。
ADD COLUMN
ADD COLUMN [IF NOT EXISTS] name [type] [default_expr] [codec] [AFTER name_after]
DROP COLUMN
ALTER TABLE visits DROP COLUMN browser
CLEAR COLUMN
ALTER TABLE visits CLEAR COLUMN browser IN PARTITION tuple()
MODIFY COLUMN
MODIFY COLUMN [IF EXISTS] name [type] [default_expr] [TTL]
ALTER table my_test.table_name_all on cluster cluster_name MODIFY COLUMN id Int64
具體可參考官方文檔:
https://clickhouse.tech/docs/zh/sql-reference/statements/alter/