If the table does exist, it is dropped; if it does not exist, the statement has no effect. Thanks for contributing an answer to Stack Overflow! Parameters name Identifier for the table to alter. 説明 ALTER TABLEは既存のテーブルの定義を変更します。以下のようにいくつかの副構文があります。 要求されるロックレベルはそれぞれの副構文によって異なることに注意してください。 特に記述がなければACCESS EXCLUSIVEロックを取得します。複数のサブコマンドが使われるときは、それらのサ … ADD AND DROP PARTITION ADD PARTITION ALTER TABLE ADD statement adds partition to ]table_name [PURGE] IF EXISTS clause: The optional IF EXISTS clause makes the statement succeed whether or not the table exists. ALTER TABLE…DROP PARTITION命令用于删除分区和存储在这个分区上的数据。 ALTER TABLE…DROP PARTITION命令用于删除分区和存储在这个分区上的数据。当您删除一个分区时，这个分区的任何子分区也会被删除。 In Impala 2.6 and higher, Impala automatically handles creating or removing the associated folders when you issue ALTER TABLE statements with the ADD PARTITION or DROP PARTITION clauses. You can use PURGE option to delete data file as well along with partition metadata but it works only in Internal/ Managed tables ALTER TABLE table_name DROP [IF EXISTS] PARTITION partition_spec PURGE; But for ALTER TABLE table_name DROP [IF EXISTS] PARTITION (part_spec, ...) Example: ALTER TABLE locationTable DROP PARTITION (country = 'US'); Insert OVERWRITE This command allows you to insert or load overwrite on a specific partition. DROP TABLE [IF EXISTS] [db_name. It supports changing the comments of columns, adding columns, and reordering columns. CREATE INSERT INTO SELECT ALTER ALTER查询仅支持* MergeTree族表引擎，以及Merge表引擎和Distributed表引擎。ALT... clickhouseSQL语法 CREATE #方式1 CREATE TABLE [IF NOT EXISTS] [db. For example, : ALTER TABLE tab_name FORCE; With InnoDB, the table rebuild will only reclaim unused space (i.e. Learn how to use the ALTER TABLE syntax of the SQL language in Databricks SQL Analytics. ALTER TABLE table_name DROP [IF EXISTS] PARTITION partition_spec [, PARTITION partition_spec,...] You can delete multiple partitions at one time. It is a way of dividing a table into related parts based on the values of partitioned columns such as date, city, and department. Likewise, the IF EXISTS clause lets DROP PARTITION succeed whether or not the partition is already in the table: alter table partition_t drop if exists partition (y=2000); alter table partition_t drop if exists partition (y=1950); show partitions partition If the identifier contains spaces or special characters, the entire string must be enclosed in double quotes. In the ALTER ATTACH PART and DROP DETACHED PART query, to specify the name of a part, use string literal with a value from the name column of the system.detached_parts table. For. Using partition, it is easy to query a portion of the data. ALTER TABLE tab_name ENGINE = InnoDB; In MariaDB 10.0 and later, the FORCE option can be used instead. Hive organizes tables into partitions. Syntax: [ database_name. ] Separate them with commas (,). ALTER TABLE cities ATTACH PARTITION cities_ab FOR VALUES IN ('a', 'b'); 要把一个分区挂接到一个哈希分区表上： ALTER TABLE orders ATTACH PARTITION orders_p4 FOR VALUES WITH (MODULUS 4, REMAINDER 3); 要把一个默认分区挂接到一个 Please be sure to answer the question.Provide details and share your research! Drop column zip from the users table if table users and column zip exists: ALTER TABLE IF EXISTS users DROP COLUMN IF EXISTS zip ; Rename column id to user_id in the users table: For tables that are protected by NO_DROP CASCADE, you can use the predicate IGNORE PROTECTION to drop a specified partition or set of partitions (for example, when splitting a table between two Hadoop clusters). ALTER TABLE table_name DROP [IF EXISTS] PARTITION partition_spec[, PARTITION partition_spec, ...] [IGNORE PROTECTION] [PURGE]; -- (Note: PURGE available in Hive 1.2.0 and later, IGNORE PROTECTION not available 2.0.0 and later) table_name COLUMNS ( col_spec ) Specifies the column to be altered or be changed. HI @Heri,Here I just wanna add some points. Rename a partition: ALTER TABLE sales RENAME PARTITION FOR ('2016-01-01') TO jan08; Drop the first (oldest) partition in a range sequence: ALTER TABLE sales DROP PARTITION FOR (RANK(1)); Exchange a table into your partition design: alterColumnAction Change column’s definition. The ALTER TABLE …DROP PARTITION command can drop partitions of a LIST or RANGE partitioned table; please note that this command does not work on a HASH partitioned table. 仅允许对使用 Hive 格式创建的表执行此操作。This operation is allowed only for tables created using the Hive format. Making statements based on opinion; back them up with You can use ALTER TABLE DROP PARTITION to drop a partition for a table. the space previously used for . Change the partitioning field values of a partition. This removes the data and metadata for this partition. Amazon S3 considerations: You can specify an s3a:// prefix on the LOCATION attribute of a table or partition to make Impala query data from the Amazon S3 filesystem. If this table is a partition, one cannot perform DROP NOT NULL on a column if it is marked NOT NULL in the parent table. IF EXISTS If the specified partition does not exists, nothing happens. Tables or partitions are sub-divided into buckets, to provide extra structure to the data that may be used for more efficient querying. Rename a partition: ALTER TABLE sales RENAME PARTITION FOR ('2016-01-01') TO jan08; Drop the first (oldest) partition in a range sequence: ALTER TABLE sales DROP PARTITION FOR (RANK(1)); Exchange a table into your partition design: For example, the following ALTER TABLE statement changes table my‑table in two ways: reassigns ownership to user Joe, and sets constraint UNIQUE on column b: REPLACE COLUMNS Replaces the column definitions of an existing table. ALTER TABLE table_name [PARTITION part_spec] SET SERDE serde_class_name [WITH SERDEPROPERTIES (key1 = val1, key2 = val2,...)] SET LOCATION And SET FILE FORMAT ALTER TABLE SET command can also be used for changing the file [ ]